Game content won't mount - almost everything is errors and checkerboard

[trent_roolz]

I don't know what's wrong, I don't get any errors related to everything being totally fucked. But anything that isn't base Gmod content shows up as errors and checkerboard.

[bohb]

Restart steam.

[Cloudhunter]

Make sure all the games are fully installed and updated. Garry required that for mounting in the latest update, but is going to drop that requirement in the next update.

[Gmod_Fan77]

Cloud, Garry has recently fixed it. All of my Source games (aside from L4D1 and 2 and the Source mods) were mounted and operational after update 120, and I didn't have to install nor run them.