Unable to start GMOD up?

I just redownloaded GMOD after not playing for a long time and I try to start it up and I get a big engine error that says:

[Steam] SteamApps() Is NULL.

I’ve tried deleting and redownloading, I’ve tried verifying the whole game. There’s no fragmentation, I’ve run a bunch of HL2 games at least once, I’ve made sure my DX and runtime libraries are up to date, Updated my video and sound card drivers, updated Windows and even tried installing/uninstalling other Source games. I can’t think of anything else.