The plugin seems like it stopped working after the 2022 June 2 Update. I see this in the rustserver-console.log:

SteamChecks was compiled successfully in 2730ms
(Filename: ./Runtime/Export/Debug/Debug.bindings.h Line: 39)

Fallback handler could not load library /home/rustserver/serverfiles/RustDedicated_Data/Mono/data-0x56158dee3850.so
Failed to initialize plugin 'SteamChecks v5.0.8' (InvalidCastException: Null object cannot be converted to a value type.)
at System.Convert.ChangeType (System.Object value, System.Type conversionType, System.IFormatProvider provider) [0x00029] in <eae584ce26bc40229c1b1aa476bfa589>:0
at System.Convert.ChangeType (System.Object value, System.Type conversionType) [0x0000c] in <eae584ce26bc40229c1b1aa476bfa589>:0
at Oxide.Core.Configuration.DynamicConfigFile.ConvertValue (System.Object value, System.Type destinationType) [0x00008] in <46ff2b534abb4b35952608167523b7ec>:0
at Oxide.Core.Configuration.DynamicConfigFile.ConvertValue[T] (System.Object value) [0x00000] in <46ff2b534abb4b35952608167523b7ec>:0
at Oxide.Core.Configuration.DynamicConfigFile.Get[T] (System.String[] path) [0x00008] in <46ff2b534abb4b35952608167523b7ec>:0
at Oxide.Plugins.SteamChecks.InitializeConfig () [0x001ab] in <a8d906cc14e649d686e0f18b3284abeb>:0
at Oxide.Plugins.SteamChecks.Init () [0x00000] in <a8d906cc14e649d686e0f18b3284abeb>:0
at Oxide.Plugins.SteamChecks.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x00225] in <a8d906cc14e649d686e0f18b3284abeb>:0
at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <e23ba2c0f246426296d81c842cbda3af>:0
at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000d8] in <46ff2b534abb4b35952608167523b7ec>:0
at Oxide.Core.Plugins.CSPlugin.HandleAddedToManager (Oxide.Core.Plugins.PluginManager manager) [0x00043] in <46ff2b534abb4b35952608167523b7ec>:0
(Filename: ./Runtime/Export/Debug/Debug.bindings.h Line: 39)

Unloaded plugin Steam Checks v5.0.8 by Shady14u
(Filename: ./Runtime/Export/Debug/Debug.bindings.h Line: 39)

No previous version to rollback plugin: SteamChecks
(Filename: ./Runtime/Export/Debug/Debug.bindings.h Line: 39)

Your configuration file appears to be invalid.

The quick response is appreciate, Wulf. Backed up the old config and reloaded the plugin to generate a new one. Updated the settings and it's working now. Unsure why that config seems to have been working until now. It looks like these are the lines that weren't in the old config file:

"CheckPlayersOnRespawn": true,
"DiscordRolesToMention": [],
"discordWebHookUrl": "",

Sorry for the delay.. Are you all set now?

Im getting this error. 

Failed to initialize plugin 'SteamChecks v5.0.8' (InvalidCastException: Null object cannot be converted to a value type.) at System.Convert.ChangeType (System.Object value, System.Type conversionType, System.IFormatProvider provider) [0x00029] in :0 at System.Convert.ChangeType (System.Object value, System.Type conversionType) [0x0000c] in :0 at Oxide.Core.Configuration.DynamicConfigFile.ConvertValue (System.Object value, System.Type destinationType) [0x00008] in <99d545163fdd4d57a562df7989f2ca0a>:0 at Oxide.Core.Configuration.DynamicConfigFile.ConvertValue[T] (System.Object value) [0x00000] in <99d545163fdd4d57a562df7989f2ca0a>:0 at Oxide.Core.Configuration.DynamicConfigFile.Get[T] (System.String[] path) [0x00008] in <99d545163fdd4d57a562df7989f2ca0a>:0 at Oxide.Plugins.SteamChecks.InitializeConfig () [0x00026] in <2ae61b7043f34da1b2e26482074bc273>:0 at Oxide.Plugins.SteamChecks.Init () [0x00000] in <2ae61b7043f34da1b2e26482074bc273>:0 at Oxide.Plugins.SteamChecks.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x00225] in <2ae61b7043f34da1b2e26482074bc273>:0 at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in :0 at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000d8] in <99d545163fdd4d57a562df7989f2ca0a>:0 at Oxide.Core.Plugins.CSPlugin.HandleAddedToManager (Oxide.Core.Plugins.PluginManager manager) [0x00043] in <99d545163fdd4d57a562df7989f2ca0a>:0