Big Probleme " authentating with Steam "

Hello , So here it make 4 days when I try to connect to any server GMOD I have this message that never disparrait .

SCREEN : http://image.noelshack.com/fichiers/2016/12/1459071085-capture.png

I have already tried :

  • Reinstall GMOD
  • Restart Steam
  • Open GMOD by admin
  • Open Steam by Admin

And still nothing. Know that I have to play an hour before everything was working and suddenly happened. Please Help me THANKS