Addons don't work

It seems time to time whenever I really want an addon to work, it never does.
Heres what happens. I would download a mod, and if that mod doesn’t work it never will. It would say on the bottom it is downloading every single time I open gmod. Once it is done downloading, it doesn’t work. It just never appears. Does anybody know how to fix this? I’ve checked in my addons folder, and the addons that aren’t working aren’t there. Does anyone know how to fix this? I’ve uninstalled and installed the mods ingame 2 times and out of game 1 time.

Yeah I have the same problem and I can’t see anywhere how to fix, but you are not alone !