{
  "A": {
    "Oxide Group": "Newcomer",
    "Playtime": 1.0
  },
  "B": {
    "Oxide Group": "Newbie",
    "Playtime": 5
  },
  "C": {
    "Oxide Group": "Noob",
    "Playtime": 15.0
  },
  "D": {
    "Oxide Group": "Amateur",
    "Playtime": 50.0
  },
  "E": {
    "Oxide Group": "Provisional",
    "Playtime": 75.0
  },
  "G": {
    "Oxide Group": "Hardcase",
    "Playtime": 125.0
  },
  "H": {
    "Oxide Group": "Professional",
    "Playtime": 260.0
  },
  "I": {
    "Oxide Group": "Elite",
    "Playtime": 500.0
  },
  "J": {
    "Oxide Group": "Legend",
    "Playtime": 750.0
  },
  "Settings": {
    "Ignore Admins": false
  }
}​

[
  {
    "GroupName": "default",
    "Priority": 0,
    "Title": {
      "Text": "[Player]",
      "Color": "#55aaff",
      "Size": 15,
      "Hidden": true,
      "HiddenIfNotPrimary": false
    },
    "Username": {
      "Color": "#55aaff",
      "Size": 15
    },
    "Message": {
      "Color": "white",
      "Size": 15
    },
    "Format": {
      "Chat": "{Title} {Username}: {Message}",
      "Console": "{Title} {Username}: {Message}"
    }
  },
  {
    "GroupName": "newcomer",
    "Priority": 0,
    "Title": {
      "Text": "[newcomer]",
      "Color": "#55aaff",
      "Size": 15,
      "Hidden": false,
      "HiddenIfNotPrimary": false
    },
    "Username": {
      "Color": "#55aaff",
      "Size": 15
    },
    "Message": {
      "Color": "white",
      "Size": 15
    },
    "Format": {
      "Chat": "{Title} {Username}: {Message}",
      "Console": "{Title} {Username}: {Message}"
    }
  },
  {
    "GroupName": "newbie",
    "Priority": 1,
    "Title": {
      "Text": "[newbie]",
      "Color": "#55aaff",
      "Size": 15,
      "Hidden": false,
      "HiddenIfNotPrimary": false
    },
    "Username": {
      "Color": "#55aaff",
      "Size": 15
    },
    "Message": {
      "Color": "white",
      "Size": 15
    },
    "Format": {
      "Chat": "{Title} {Username}: {Message}",
      "Console": "{Title} {Username}: {Message}"
    }
  },
  {
    "GroupName": "noob",
    "Priority": 2,
    "Title": {
      "Text": "[noob]",
      "Color": "#55aaff",
      "Size": 15,
      "Hidden": false,
      "HiddenIfNotPrimary": false
    },
    "Username": {
      "Color": "#55aaff",
      "Size": 15
    },
    "Message": {
      "Color": "white",
      "Size": 15
    },
    "Format": {
      "Chat": "{Title} {Username}: {Message}",
      "Console": "{Title} {Username}: {Message}"
    }
  },
  {
    "GroupName": "amateur",
    "Priority": 3,
    "Title": {
      "Text": "[amateur]",
      "Color": "#55aaff",
      "Size": 15,
      "Hidden": false,
      "HiddenIfNotPrimary": false
    },
    "Username": {
      "Color": "#55aaff",
      "Size": 15
    },
    "Message": {
      "Color": "white",
      "Size": 15
    },
    "Format": {
      "Chat": "{Title} {Username}: {Message}",
      "Console": "{Title} {Username}: {Message}"
    }
  },
  {
    "GroupName": "provisional",
    "Priority": 4,
    "Title": {
      "Text": "[provisional]",
      "Color": "#55aaff",
      "Size": 15,
      "Hidden": false,
      "HiddenIfNotPrimary": false
    },
    "Username": {
      "Color": "#55aaff",
      "Size": 15
    },
    "Message": {
      "Color": "white",
      "Size": 15
    },
    "Format": {
      "Chat": "{Title} {Username}: {Message}",
      "Console": "{Title} {Username}: {Message}"
    }
  },
  {
    "GroupName": "hardcase",
    "Priority": 5,
    "Title": {
      "Text": "[hardcase]",
      "Color": "#55aaff",
      "Size": 15,
      "Hidden": false,
      "HiddenIfNotPrimary": false
    },
    "Username": {
      "Color": "#55aaff",
      "Size": 15
    },
    "Message": {
      "Color": "white",
      "Size": 15
    },
    "Format": {
      "Chat": "{Title} {Username}: {Message}",
      "Console": "{Title} {Username}: {Message}"
    }
  },
  {
    "GroupName": "professional",
    "Priority": 6,
    "Title": {
      "Text": "[professional]",
      "Color": "#55aaff",
      "Size": 15,
      "Hidden": false,
      "HiddenIfNotPrimary": false
    },
    "Username": {
      "Color": "#55aaff",
      "Size": 15
    },
    "Message": {
      "Color": "white",
      "Size": 15
    },
    "Format": {
      "Chat": "{Title} {Username}: {Message}",
      "Console": "{Title} {Username}: {Message}"
    }
  },
  {
    "GroupName": "elite",
    "Priority": 7,
    "Title": {
      "Text": "[elite]",
      "Color": "#55aaff",
      "Size": 15,
      "Hidden": false,
      "HiddenIfNotPrimary": false
    },
    "Username": {
      "Color": "#55aaff",
      "Size": 15
    },
    "Message": {
      "Color": "white",
      "Size": 15
    },
    "Format": {
      "Chat": "{Title} {Username}: {Message}",
      "Console": "{Title} {Username}: {Message}"
    }
  },
  {
    "GroupName": "legend",
    "Priority": 8,
    "Title": {
      "Text": "[legend]",
      "Color": "#55aaff",
      "Size": 15,
      "Hidden": false,
      "HiddenIfNotPrimary": false
    },
    "Username": {
      "Color": "#55aaff",
      "Size": 15
    },
    "Message": {
      "Color": "white",
      "Size": 15
    },
    "Format": {
      "Chat": "{Title} {Username}: {Message}",
      "Console": "{Title} {Username}: {Message}"
    }
  }
]

above is my better chat groups  and playerrankings config have i done something wrong as this plugin will just not work for me

and would setting a playerrank playtime to 0 hours automatically give them a rank

There are betters ways to put players in a group such as setting a default group. But as far as your problem goes, I really cannot tell what the issue is without some extra information. Do you have an additional playtime tracking plugin that is compatible with PlayerRankings? I also see that some of the names of the PR configs and BetterChat configs do not match, so are ranks working for some but not for others?

No i wouldnt as your first rank is for 5 hours on the server. if you set it to 0 hours then anyone who joins your server to take a look would get a rank and you would end up with a lot of unused players with that rank in your data file.
Your default and your first rank have the same priority number.
here is a copy of mine (been using it with no problems for years with connectdb plugin)
I have been told my priorities are wrong but they work for me

[
  {
    "GroupName": "default",
    "Priority": 1,
    "Title": {
      "Text": "[]",
      "Color": "#00ffffff",
      "Size": 17,
      "Hidden": true,
      "HiddenIfNotPrimary": true
    },
    "Username": {
      "Color": "#ffff00ff",
      "Size": 17
    },
    "Message": {
      "Color": "#ffffffff",
      "Size": 17
    },
    "Format": {
      "Chat": "{Title} {Username}: {Message}",
      "Console": "{Title} {Username}: {Message}"
    }
  },
  {
    "GroupName": "Noob",
    "Priority": 4,
    "Title": {
      "Text": "[Noob]",
      "Color": "#00ffffff",
      "Size": 17,
      "Hidden": false,
      "HiddenIfNotPrimary": false
    },
    "Username": {
      "Color": "#ffff00ff",
      "Size": 17
    },
    "Message": {
      "Color": "#ffffffff",
      "Size": 17
    },
    "Format": {
      "Chat": "{Title} {Username}: {Message}",
      "Console": "{Title} {Username}: {Message}"
    }
  },
  {
    "GroupName": "Newbie",
    "Priority": 3,
    "Title": {
      "Text": "[Newbie]",
      "Color": "#00ffffff",
      "Size": 17,
      "Hidden": false,
      "HiddenIfNotPrimary": false
    },
    "Username": {
      "Color": "#ffff00ff",
      "Size": 17
    },
    "Message": {
      "Color": "#ffffffff",
      "Size": 17
    },
    "Format": {
      "Chat": "{Title} {Username}: {Message}",
      "Console": "{Title} {Username}: {Message}"
    }
  },
  {
    "GroupName": "Spaz",
    "Priority": 2,
    "Title": {
      "Text": "[Spaz]",
      "Color": "#00ffffff",
      "Size": 17,
      "Hidden": false,
      "HiddenIfNotPrimary": false
    },
    "Username": {
      "Color": "#ffff00ff",
      "Size": 17
    },
    "Message": {
      "Color": "#ffffffff",
      "Size": 17
    },
    "Format": {
      "Chat": "{Title} {Username}: {Message}",
      "Console": "{Title} {Username}: {Message}"
    }
  },
  {
    "GroupName": "Learner",
    "Priority": 5,
    "Title": {
      "Text": "[Learner]",
      "Color": "#00ffffff",
      "Size": 17,
      "Hidden": false,
      "HiddenIfNotPrimary": false
    },
    "Username": {
      "Color": "#00ffffff",
      "Size": 17
    },
    "Message": {
      "Color": "#ffffffff",
      "Size": 17
    },
    "Format": {
      "Chat": "{Title} {Username}: {Message}",
      "Console": "{Title} {Username}: {Message}"
    }
  },
  {
    "GroupName": "Provisional",
    "Priority": 6,
    "Title": {
      "Text": "[Provisional]",
      "Color": "#00ffffff",
      "Size": 17,
      "Hidden": false,
      "HiddenIfNotPrimary": false
    },
    "Username": {
      "Color": "#00ffffff",
      "Size": 17
    },
    "Message": {
      "Color": "#ffffffff",
      "Size": 17
    },
    "Format": {
      "Chat": "{Title} {Username}: {Message}",
      "Console": "{Title} {Username}: {Message}"
    }
  },
    {
    "GroupName": "MegaMaximus",
    "Priority": 10,
    "Title": {
      "Text": "[MegaMaximus]",
      "Color": "#00ffffff",
      "Size": 17,
      "Hidden": false,
      "HiddenIfNotPrimary": false
    },
    "Username": {
      "Color": "#00ffffff",
      "Size": 17
    },
    "Message": {
      "Color": "#ffffffff",
      "Size": 17
    },
    "Format": {
      "Chat": "{Title} {Username}: {Message}",
      "Console": "{Title} {Username}: {Message}"
      }
   },
   { 
    "GroupName": "UltraMaximus",
    "Priority": 11,
    "Title": {
      "Text": "[UltraMaximus]",
      "Color": "#00ffffff",
      "Size": 17,
      "Hidden": false,
      "HiddenIfNotPrimary": false
    },
    "Username": {
      "Color": "#00ffffff",
      "Size": 17
    },
    "Message": {
      "Color": "#ffffffff",
      "Size": 17
    },
    "Format": {
      "Chat": "{Title} {Username}: {Message}",
      "Console": "{Title} {Username}: {Message}"
     }
      },
    {
    "GroupName": "SuperMaximus",
    "Priority": 12,
    "Title": {
      "Text": "[SuperMaximus]",
      "Color": "#00ffffff",
      "Size": 17,
      "Hidden": false,
      "HiddenIfNotPrimary": false
    },
    "Username": {
      "Color": "#00ffffff",
      "Size": 17
    },
    "Message": {
      "Color": "#ffffffff",
      "Size": 17
    },
    "Format": {
      "Chat": "{Title} {Username}: {Message}",
      "Console": "{Title} {Username}: {Message}"
      }
     },
   { 
    "GroupName": "Hardcase",
    "Priority": 7,  
    "Title": {
      "Text": "[Hardcase]",
      "Color": "#00ffffff",
      "Size": 17,
      "Hidden": false,
      "HiddenIfNotPrimary": false
    },
    "Username": {
      "Color": "#00ffffff",
      "Size": 17
    },
    "Message": {
      "Color": "#ffffffff",
      "Size": 17
    },
    "Format": {
      "Chat": "{Title} {Username}: {Message}",
      "Console": "{Title} {Username}: {Message}"
    }
  },
  {
    "GroupName": "Professional",
    "Priority": 8,
    "Title": {
      "Text": "[Professional]",
      "Color": "#00ffffff",
      "Size": 17,
      "Hidden": false,
      "HiddenIfNotPrimary": false
    },
    "Username": {
      "Color": "#00ffffff",
      "Size": 17
    },
    "Message": {
      "Color": "#ffffffff",
      "Size": 17
    },
    "Format": {
      "Chat": "{Title} {Username}: {Message}",
      "Console": "{Title} {Username}: {Message}"
    }
  },
{
    "GroupName": "PrimoMaximus",
    "Priority": 13,
    "Title": {
      "Text": "[PrimoMaximus]",
      "Color": "#00ffffff",
      "Size": 17,
      "Hidden": false,
      "HiddenIfNotPrimary": false
    },
    "Username": {
      "Color": "#00ffffff",
      "Size": 17
    },
    "Message": {
      "Color": "#ffffffff",
      "Size": 17
    },
    "Format": {
      "Chat": "{Title} {Username}: {Message}",
      "Console": "{Title} {Username}: {Message}"
    }
  },
{
    "GroupName": "AbsoluteMaximus",
    "Priority": 14,
    "Title": {
      "Text": "[AbsoluteMaximus]",
      "Color": "#00ffffff",
      "Size": 17,
      "Hidden": false,
      "HiddenIfNotPrimary": false
    },
    "Username": {
      "Color": "#00ffffff",
      "Size": 17
    },
    "Message": {
      "Color": "#ffffffff",
      "Size": 17
    },
    "Format": {
      "Chat": "{Title} {Username}: {Message}",
      "Console": "{Title} {Username}: {Message}"
    }
  },
  {
    "GroupName": "GetALifeMaximus",
    "Priority": 15,
    "Title": {
      "Text": "[GetALifeMaximus]",
      "Color": "#00ffffff",
      "Size": 17,
      "Hidden": false,
      "HiddenIfNotPrimary": false
    },
    "Username": {
      "Color": "#00ffffff",
      "Size": 17
    },
    "Message": {
      "Color": "#ffffffff",
      "Size": 17
    },
    "Format": {
      "Chat": "{Title} {Username}: {Message}",
      "Console": "{Title} {Username}: {Message}"
    }
  },
  {
    "GroupName": "Maximus",
    "Priority": 9,
    "Title": {
      "Text": "[Maximus]",
      "Color": "#00ffffff",
      "Size": 17,
      "Hidden": false,
      "HiddenIfNotPrimary": false
    },
    "Username": {
      "Color": "#00ffffff",
      "Size": 17
    },
    "Message": {
      "Color": "#ffffffff",
      "Size": 17
    },
    "Format": {
      "Chat": "{Title} {Username}: {Message}",
      "Console": "{Title} {Username}: {Message}"
    }
   }
  }
]​

{
  "A": {
    "Oxide Group": "Spaz",
    "Playtime": 1.0
  },
  "B": {
    "Oxide Group": "Newbie",
    "Playtime": 5.0
  },
  "C": {
    "Oxide Group": "Noob",
    "Playtime": 15.0
  },
  "D": {
    "Oxide Group": "Learner",
    "Playtime": 50.0
  },
  "E": {
    "Oxide Group": "Provisional",
    "Playtime": 75.0
  },
  "G": {
    "Oxide Group": "Hardcase",
    "Playtime": 125.0
  },
  "H": {
    "Oxide Group": "Professional",
    "Playtime": 260.0
  },
  "I": {
    "Oxide Group": "Maximus",
    "Playtime": 500.0
  },
  "J": {
    "Oxide Group": "MegaMaximus",
    "Playtime": 750.0
  },
  "K": {
    "Oxide Group": "UltraMaximus",
    "Playtime": 1000.0
  },
  "L": {
    "Oxide Group": "SuperMaximus",
    "Playtime": 1500.0
  },
  "M": {
    "Oxide Group": "PrimoMaximus",
    "Playtime": 3000.0
  },
  "N": {
    "Oxide Group": "GrandMaximus",
    "Playtime": 4500.0
  },
  "O": {
    "Oxide Group": "AbsoluteMaximus",
    "Playtime": 6000.0
  },
  "p": {
    "Oxide Group": "GetALifeMaximus",
    "Playtime": 10000.0
  },
  "Settings": {
    "Ignore Admins": false
  }
}​

I use the ranks for server rewards (permissions for plugins and extra kits)