WAW zombies crashes every time when joining server

[Tikoz]

Hello guys, I recently downloaded the plutonium T4 game to play zombies.
the game works fine when I play solo even when using mods and custom maps, however every time I click connect on a server the game goes back to main menu and closes instantly.

keep in mind that I tried to join multiplayer servers and it works fine.

If anyone knows how to fix this please let me know and thanks.