Gmod not starting up

Incredibly weird.
It started when I rolled back my drivers to finish playing Omikron : The Nomad soul.
I installed the latest drivers , but couldn’t run Gmod.
HL2 Runs , so does Episode 2 , but Gmod just refuses to run.

I’ve done a clean Install of gmod - Still won’t run.
If anyone has ideas , please tell me .



No help?