legacy addons aren't working

Recently, all my non-workshop addons have stopped working. They don’t even show up in the spawn menus, even if I just place the materials, models, lua and stuff in the Garry’s Mod common folder. All the addons downloaded from the workshop work fine, but not the ones I install manually. Any help?

When you start the game up in console does it say “Adding file system addon”?

The only thing it says about any addons is “Addons have changed - remounting”