Broken Steam "account used elsewhere" error prevents me from joining any server?

So if I join any server, I will get this error:

No, my account is not used on another computer. I already tried logging out and logging back in, it didn’t work. I also already checked my lua/autorun files and there’s nothing suspicious in it.
So uhh, anyone got ideas?

Uh, logging out and in is a temporary fix I believe, since the hack can do that same. also it wouldn’t be a lau file

Try deleting clientregistry.blob.

I’m getting the exact same error. Only with garrysmod though.

Yeah, this error doesn’t come out in any other games except for Gmod, so this has to be a Gmod problem. Anyone got ideas?

Restart Steam / PC / Delete clientregistry.blob.

Is anyone Getting This for Zombie Panic! Source, it is the only game that i am getting that error message