Failed to call hook 'PlayerAdministrationBanUserCallback' on plugin 'PlayerAdministration v1.6.2' (NullReferenceException: Object reference not set to an instance of an object)
at Oxide.Plugins.PlayerAdministration.PlayerAdministrationBanUserCallback (Oxide.Core.Libraries.Covalence.IPlayer aPlayer, System.String aCommand, System.String[] aArgs) [0x00247] in <a2d527b9c1f34a63b7edf7a44ba844d7>:0
at Oxide.Plugins.PlayerAdministration.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x01504] in <a2d527b9c1f34a63b7edf7a44ba844d7>:0
at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <80b90e8213db44b29ec2d4111764172c>:0
at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000d8] in <ec05e0208c9149bba43236ca58fea105>:0
at Oxide.Core.Plugins.Plugin.CallHook (System.String hook, System.Object[] args) [0x00060] in <ec05e0208c9149bba43236ca58fea105>:0

Failed to call hook 'PlayerAdministrationBanUserCallback' on plugin 'PlayerAdministration v1.6.2' (NullReferenceException: Object reference not set to an instance of an object)
  at Oxide.Plugins.PlayerAdministration.PlayerAdministrationBanUserCallback (Oxide.Core.Libraries.Covalence.IPlayer aPlayer, System.String aCommand, System.String[] aArgs) [0x00247] in :0
  at Oxide.Plugins.PlayerAdministration.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x01504] in :0
  at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <80b90e8213db44b29ec2d4111764172c>:0
  at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000d8] in :0
  at Oxide.Core.Plugins.Plugin.CallHook (System.String hook, System.Object[] args) [0x00060] in :0

Hello, same error when i am trying to ban players

I did a couple of fixes, might wanne give them a try:
https://github.com/thibmo/PlayerAdministration/releases/tag/1.6.03