Steam Validation rejected InGame

I was playing a server on gmod when i crashed or disconnected. When i try to rejoin it says to me steam validation rejected. after a short while it will let me back on. The server is called [CA] Fight to survive.

it is a bug, steam bug, it happens to me all the time.
Every first server i join, and sometimes it happens randomly. Steam just sucks.

Any way to fix it?