Please try following steps below to completely re-install Action. You will need your serial number to activate your product again.
1. Uninstall Action!
2. Press Start and then type "Regedit" in search and press Enter.
3. Go to the following path: HKEY_CURRENT_USER/Software/Mirillis/
4. Remove Action! catalog.
5. Reboot your PC.
6. Install Action! again. Make sure that your installer file comes from official website - www.mirillis.com
(if you have not purchased Action! through Steam).
You can activate Action! with the same serial number as before.
These steps should restore your Action! settings to default.