You can resolve this issue by reinstalling the application.
- Quit GarageBand or Logic Pro X.
- In the finder, click the Go menu and choose Applications.
- Drag the application icon to the Trash.
- Open the Mac App Store.
- Click the Purchases tab.
- Sign in to the Mac App Store using the Apple ID you first used to install GarageBand or Logic Pro X.
- Look for GarageBand or Logic Pro X in the list of purchased applications. If you don't see it in the list, make sure it's not hidden.
- Click Install to download and install the application.