something wrong with my config? never had this before.

Web request callback raised an exception (ArgumentNullException: Value cannot be null.
Parameter name: source)
  at System.Linq.Enumerable.Count[TSource] (System.Collections.Generic.IEnumerable`1[T] source) [0x0000d] in <351e49e2a5bf4fd6beabb458ce2255f3>:0
  at Oxide.Plugins.ServerArmour.IsBanned (System.String steamid) [0x00045] in <664758c7272b4e93ba331f23b53c3020>:0
  at Oxide.Plugins.ServerArmour.KickIfBanned (Oxide.Plugins.ServerArmour+ISAPlayer isaPlayer) [0x00017] in <664758c7272b4e93ba331f23b53c3020>:0
  at Oxide.Plugins.ServerArmour+<_webCheckPlayer>c__AnonStorey0.<>m__0 (System.Int32 code, System.String response) [0x000c4] in <664758c7272b4e93ba331f23b53c3020>:0
  at Oxide.Core.Libraries.WebRequests+WebRequest.<OnComplete>b__42_0 () [0x00034] in <ac41dd3599754d448b8c218b34645820>:0

Just downloaded it and the following I have for you as output

[Server Armour] Added new field to config: Auto Kick: Max allowed Game bans
[Server Armour] Server Armour is being initialized.
[Server Armour] Server Armour finished initializing.
Loaded plugin Server Armour v0.2.5 by Pho3niX90
ExType: JsonSerializationException
Web request callback raised an exception (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 <437ba245d8404784b9fbab9b439ac908>:0
  at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.EnsureType (Newtonsoft.Json.JsonReader reader, System.Object value, System.Globalization.CultureInfo culture, Newtonsoft.Json.Serialization.JsonContract contract, System.Type targetType) [0x0007c] in <7126fb4f5c5b40029458a4f975f98d13>:0
ExType: JsonSerializationException
Web request callback raised an exception in 'ServerArmour v0.2.5' plugin (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 <437ba245d8404784b9fbab9b439ac908>:0
  at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.EnsureType (Newtonsoft.Json.JsonReader reader, System.Object value, System.Globalization.CultureInfo culture, Newtonsoft.Json.Serialization.JsonContract contract, System.Type targetType) [0x0007c] in <7126fb4f5c5b40029458a4f975f98d13>:0

Web request callback raised an exception in 'ServerArmour v0.2.6' plugin (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 <437ba245d8404784b9fbab9b439ac908>:0 
  at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.EnsureType (Newtonsoft.Json.JsonReader reader, System.Object value, System.Globalization.CultureInfo culture, Newtonsoft.Json.Serialization.JsonContract contract, System.Type targetType) [0x0007c] in <7126fb4f5c5b40029458a4f975f98d13>:0 ​

Web request callback raised an exception (ArgumentNullException: Value cannot be null.
Parameter name: source)
  at System.Linq.Enumerable.Count[TSource] (System.Collections.Generic.IEnumerable`1[T] source) [0x0000d] in <351e49e2a5bf4fd6beabb458ce2255f3>:0
  at Oxide.Plugins.ServerArmour.IsBanned (System.String steamid) [0x00045] in <a4a839a0ba69403a839b0dc79237384d>:0
  at Oxide.Plugins.ServerArmour.KickIfBanned (Oxide.Plugins.ServerArmour+ISAPlayer isaPlayer) [0x00017] in <a4a839a0ba69403a839b0dc79237384d>:0
  at Oxide.Plugins.ServerArmour+<_webCheckPlayer>c__AnonStorey0.<>m__0 (System.Int32 code, System.String response) [0x00136] in <a4a839a0ba69403a839b0dc79237384d>:0​

I have the same errors. I think about special characters too, 
So I add 1 line debug log on userconnected and onuserdisconnected.

At the next error I will post the log with nickname and steamid64.

Regards

10:43 [Info] [Server Armour] IcoPlays (76561198881970671) Disconnected
10:43 [Error] Web request callback raised an exception (ArgumentNullException: Value cannot be null.
Parameter name: source)
  at System.Linq.Enumerable.Count[TSource] (System.Collections.Generic.IEnumerable`1[T] source) [0x0000d] in <351e49e2a5bf4fd6beabb458ce2255f3>:0
  at Oxide.Plugins.ServerArmour.IsBanned (System.String steamid) [0x00045] in <bdb794842fe64ebf95d58bbb81e8d8a5>:0
  at Oxide.Plugins.ServerArmour.KickIfBanned (Oxide.Plugins.ServerArmour+ISAPlayer isaPlayer) [0x00017] in <bdb794842fe64ebf95d58bbb81e8d8a5>:0
  at Oxide.Plugins.ServerArmour+<_webCheckPlayer>c__AnonStorey0.<>m__0 (System.Int32 code, System.String response) [0x00136] in <bdb794842fe64ebf95d58bbb81e8d8a5>:0
  at Oxide.Core.Libraries.WebRequests+WebRequest.<OnComplete>b__42_0 () [0x00034] in <ac41dd3599754d448b8c218b34645820>:0

Web request callback raised an exception (ArgumentNullException: Value cannot be null.
Parameter name: source)
  at System.Linq.Enumerable.Count[TSource] (System.Collections.Generic.IEnumerable`1[T] source) [0x0000d] in <351e49e2a5bf4fd6beabb458ce2255f3>:0 
  at Oxide.Plugins.ServerArmour.IsBanned (System.String steamid) [0x00045] in <abd6e21b82a348ddb5c3b7bd2e246643>:0 
  at Oxide.Plugins.ServerArmour.KickIfBanned (Oxide.Plugins.ServerArmour+ISAPlayer isaPlayer) [0x00017] in <abd6e21b82a348ddb5c3b7bd2e246643>:0 
  at Oxide.Plugins.ServerArmour+<_webCheckPlayer>c__AnonStorey0.<>m__0 (System.Int32 code, System.String response) [0x00136] in <abd6e21b82a348ddb5c3b7bd2e246643>:0 
  at Oxide.Core.Libraries.WebRequests+WebRequest.<OnComplete>b__42_0 () [0x00034] in <ac41dd3599754d448b8c218b34645820>:0 ​

Just downloaded v0.3.0 and got the same: (First install so no other files were on the server)

**Edit looks like a different error actually.

ExType: JsonSerializationException
Web request callback raised an exception (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 <437ba245d8404784b9fbab9b439ac908>:0
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.EnsureType (Newtonsoft.Json.JsonReader reader, System.Object value, System.Globalization.CultureInfo culture, Newtonsoft.Json.Serialization.JsonContract contract, System.Type targetType) [0x0007c] in <7126fb4f5c5b40029458a4f975f98d13>:0

ESoTeRiC

Same errors

Which one?