Updated Discord Extension to 2.0+ and all my discord plugins (discord auth and status and rustcord) but for some reason Rustcord gives this error... 
(15:23:15) | Failed to call hook 'OnDiscordClientCreated' on plugin 'Rustcord v3.0.0' (NullReferenceException: Object reference not set to an instance of an object)

at Oxide.Plugins.Rustcord.OnDiscordClientCreated () [0x0000b] in <5b7bd0f01bb7481b8c790c6b4c9bb8fe>:0

at Oxide.Plugins.Rustcord.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x005e1] in <5b7bd0f01bb7481b8c790c6b4c9bb8fe>:0

at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <31122a27a2414cd799150f8677cf39d4>:0

at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000d8] in <0fbce81d88d64454b3e7abb24df7026b>:0

at Oxide.Core.Plugins.Plugin.CallHook (System.String hook, System.Object[] args) [0x00060] in <0fbce81d88d64454b3e7abb24df7026b>:0

(15:23:15) | Unloaded plugin Rustcord v3.0.0 by Kirollos & OuTSMoKE

(15:23:15) | No previous version to rollback plugin: Rustcord

Did you restart your server after updating the Discord Ext dll? The server will not load the new dll until you restart.

I stopped it and put extension then started the server again...

I'm getting the same error on Rustcord v3.0.1, and looked at server startup log to verify Discord Ext dll (v2.0.2) is being loaded "Loaded extension Discord v2.0.2 by PsychoTea & DylanSMR & Tricky & Kirollos & MJSU"

Edit - I deleted the old oxide/config/Rustcord.json and lang/en/Rustcord.json files and it got rid of the plugin loading error on server restart. I then compared old to new config to adjust to all the changes.