gmod "verified" help

When I try to launch Garry’s Mod, either from the Steam client or from the desktop shortcut, Garry’s Mod says it’s preparing to start, but then it switches to a verifying windows, and then it says verified 100% and I click close but the game does not start. I try again, but the same thing happens. I know I can run Garry’s Mod on my pc, just what am I missing?

Help me please!

Guys c’mon! THis is a simple question! It has nothing to do with errors or scripts! PLEASE?

Restart Steam, Restart your PC, Reinstall Gmod, Reinstall Steam.