Here is the critical mechanic: If the user has never "purchased" GarageBand before (even when it was free), they may run into issues. However, if the Apple ID has ever claimed GarageBand on any Mac or iOS device, the App Store will check the OS version. Since the current live version is incompatible, the server automatically offers the —specifically, GarageBand 10.1.6 or 10.2.0 (depending on the exact build date of 10.11.6).
GarageBand will now appear in your history. Click , and accept the prompt to download the last compatible version. Method 3: Restoring via Time Machine or iLife Disks Garageband Mac Os X El Capitan 10.11.6 Download
(cloud symbol) next to GarageBand. The App Store will automatically detect that you are running El Capitan and offer to download the most recent compatible version for your operating system. Here is the critical mechanic: If the user