My 10.11.6 mac won't load Garage Band after upgrade
How to get a copy of Garage Band to re-install. I up-graded to 10.11.6 and now it won't load.
iMac, OS X 10.11
Try to restore GarageBand from the backup you made of your Mac before you upgraded to OS X 10.11.6 .
The current GarageBand version at the App Store (GarageBand 10.4.3) requires macOS 11.0 or later and cannot be downloaded on older System Versions.
Try, if you can get GarageBand to download from the AppStore, if you reinstall it from your purchase history. Open the fourth tab "Purchases" at the AppStore and look for GarageBand in the history of previous purchases. Either GarageBand '11 (version 6.0.5) or a previous purchase of GarageBand 10 might reinstall a compatible version.