Hi Stubbzyy97
I'm currently experiencing the same problem, the worst thing is that I've looked on all the forums and still nothing about resolving this issue has arisen, I have reason to believe the specs of the PC aren't the problem, I play Attack of the B-team on a 5 year old, worn out laptop and the problem only came about today for me, no warning; just out of no where, I couldn't join a server, however I can still play on Singleplayer worlds. I'm not sure if this to do with the DDOS attacks on servers or if it's to do with this version of Attack of the B-team affecting my laptop. I'm osrry I couldn't provide a solution, it's just good to know that I'm not the only one having this problem.