A known compatibility quirk between GarageBand 6.0.5 and High Sierra’s security/privacy changes. Apple officially acknowledges this behavior.

When trying to update to GarageBand 6.0.5 via the App Store’s Updates tab, you see an error message saying the item is not available.

If you want to get this vintage software up and running, let me know: What your computer is currently running? Whether you have an Intel or Apple Silicon processor?

If you are running a newer version of macOS, I can help you find alternatives that work on newer systems. Tell me which macOS version you are running if you'd like guidance! YouTube·The GarageBand Guide Can You Download an Older Version of GarageBand?

Many users actively seek out version 6.0.5 over the latest App Store versions for several specific reasons: