PC [HELP] The game doesn't let my friend use his usual character

[Jouster26]

Me and my friends have been playing for about two weeks now but since the 1.5.4 one of them can't choose his usual character or any other before this patch hi had to use third party software in order to join our game even if hi bought the game on steam it just didn't let him join normaly until 1.5.4 but them it didn't let him choose his normal character.
We are all playing on pc and steam

 

[Odin]

Unfortunately that's likely a result of that software making them appear to be joining from a different IP.