The command /skin add shortname id is not working for me. It always retrieves the skins help menu. I have tried it ingame and rcon and same thing happens. Am i doing something wrong or is in fact not working at the moment?

Failed to call hook 'OnItemAddedToContainer' on plugin 'Skins v2.2.2' (NullReferenceException: Object reference not set to an instance of an object)
  at Oxide.Plugins.Skins+ContainerController.DrawUI (System.Int32 page) [0x0003f] in <dde2c2dd300548e88ed8532c9b6ff207>:0 
  at Oxide.Plugins.Skins+ContainerController.UpdateContent (System.Int32 page) [0x00205] in <dde2c2dd300548e88ed8532c9b6ff207>:0 
  at Oxide.Plugins.Skins.OnItemAddedToContainer (ItemContainer itemContainer, Item item) [0x000a2] in <dde2c2dd300548e88ed8532c9b6ff207>:0 
  at Oxide.Plugins.Skins.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x002f3] in <dde2c2dd300548e88ed8532c9b6ff207>:0 
  at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <09575a60985045248bcb43b20faeeb99>:0 
  at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000d8] in <bae5f1223fce49c493b01571c99dce02>:0 
  at Oxide.Core.Plugins.Plugin.CallHook (System.String hook, System.Object[] args) [0x00060] in <bae5f1223fce49c493b01571c99dce02>:0 ​

What command are you using exactly? Include the shortname and skinid.

This command was used.

/skin add hazmatsuit 252490

252490 isn't a skinid

Sorry for the trouble, but where is the skin ID for this URL?
https://steamcommunity.com/market/listings/252490/Spacesuit

It's not a skin, it's a separate item.
hazmatsuit.spacesuit

Thx!!