Reinstall Final Cut Pro
Follow these instructions to reinstall Final Cut Pro via the App Store:
Navigate to the Applications folder on your system. From Finder's "Go" menu, select "Applications"
Delete Final Cut Pro from your system. One way is to drag the app icon to the Trash
Launch the App Store app, search the application title & download the app
You can also locate the app under the "Purchased" section of your account in the app store. Make sure you have signed in with the same account that was originally used to purchase the app.
Reinstalling the application can often remove certain problems that may occur over time.