Garageband won't open...

Hi bostonbrad,

Welcome to Apple Support Communities. To troubleshoot the inability of opening an app, like GarageBand, we recommend to follow these helpful steps:

If you aren’t an administrator of your Mac, the administrator may be preventing you from using the app. Contact the administrator of your Mac.

You may be trying to open an app that is not registered with Apple by an identified developer. If you want, you can open an app from an unidentified developer. 

If you recently installed a new version of macOS, some apps may need to be updated or reinstalled. See Install and uninstall apps from the internet or disc.

That information is outlined in this article: If you can’t open an app on Mac

Best regards.

Hi bostonbrad,

Thanks for getting back to us. Are you able to get the older version from the Store drop down menu > View My Account?

If not, then Garage Band for High Sierra would no longer be available.

Have a fantastic day!