Stuck on 'Authenticating with Steam'. (ONLY ONE PLAYER AT A TIME)

So for some reason only one player can be on my server at a time. The others who try to join it get stuck on ‘Authenticating with steam’.
It literally stays on that forever.

Does anyone know how to fix this?

Edit: Fixed this, was a command line issue.

Bump, really need to get this solved. Please help!