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: if a message says Cullibrate can't be opened, open System Settings → Privacy & Security and choose Open Anyway.