I havent been able to join any servers for a few months. Im on a wired connection with a 15Mb/s internet speed.
i don’t know if it will fix it for u, but when i can’t join any server, i just verify the game cache on steam. then i start the game again and it works, sometimes it needs and extra restart =/
it easy just: right-click in the game on steam > select properties > Local Files > verify integrity of game cache.
extra: i am on windows 10.