Disconnecting From Server After 5 Seconds

Hello, new guy here, I downloaded the game client with Legion models from here, so my problem is that whenever I try to log into any server I get disconnected after 5 seconds, I know it's not my internet connection because everything else works just fine, plus I tried a different private server and I didn't get disconnected at all, I don't get disconnected while playing in retail either, ports are open and WoW is allowed in Firewall, I really want to play here with my friend and I don't know what's causing the problem someone please help.