Cant join servers?

Everytime I try to join any server it kicks me and says 'Could not authenticate steam'

How do I fix this?

Also I had Mathews hack in my library but I didn't inject and I have the original assembly.dll

Well, If you haven't actually bought the game, It won't work, they now have a Server

FIXED: I was using my other steam account and family sharing from my main, you can't do that anymore apparently.