If Cullibrate won't open, work through these steps in order. Nine times out of ten it's fixed by step 2.
- Restart your machine. This clears any stale OS handles.
- Reinstall Cullibrate. Download a fresh copy from your account and reinstall over the top — your preferences are preserved.
- Check disk space. Cullibrate needs at least 2 GB free on your primary drive.
- On macOS: right-click Cullibrate → Open (once). Some Gatekeeper edge cases only clear after a right-click open.