Can not join my friend's game at COD5

[efendibulluk]

Hi everyone im so new on this. We did everything bu when i double click to my friends name we can not join the same game. Can you help me pls ?

[Resxt]

Firewall blocking or bad port forward rule or the host is not in-game when being joined then. Show screenshots
https://plutonium.pw/docs/custom-games/