Can't connect to multiplayer on steam

Everytime I try to connect to multiplayer I get this message:

Does anyone knows what could it be?

Can someone at least point me who I can talk to try solving my problem?

Outside of mods, nobody takes care of this game anymore bro, sorry, wish I could help you.

Thats a bit sad, me and some friends were thinking of coming back to play.

Try searching for a topic on steam version. I believe I’ve seen this problem on the forum before.