1. Open your G.A.M.M.A. Launcher as admin
2. Enable the top 4 boxes under the installation buttons, make sure they're selected
3. Click "Install / Update G.A.M.M.A." and wait for the install process to be done
4. Open your MO2 and check if you have any red crosses, make also sure that you have #π577-mods-in-mo2
This procedure does NOT remove saves, you're NOT going to redownload everything from scratch and it WON'T delete your progress, your save is... safe.
The launcher will simply check every mod in the pack, reinstall/fix them if you have red crosses and any mod that need to be updated, will be updated, that's it, nothing else.
In case you want to save your in-game or MCM settings (because the launcher will revert them back to default), type !backup in #π€bot-commands.