I'm using a mid-2011 Mac Mini on OS Sierra and there is a GarageBand update showing in the App Store, but when I try to update it I keep getting an error message that says it can't update because it "was refunded or purchased with a different Apple ID". I have no idea what it's talking about, the program came with this Mac Mini and I am the only owner.
Mac mini, macOS 10.12
Try starting up in Safe Mode, as per > Use safe mode to isolate issues with your Mac - Apple Support
then see if you can update the macOS and then GarageBand.
In addition, check to see if you are logged into your Admin User Account and not just an Other user account.
Your 2011 MacMini can run up to 10.13 High Sierra.
see > How to upgrade to macOS High Sierra - Apple Support
With that in mind, upgrade to 10.13.6 High Sierra and then update the GarageBand app.
I have not been able to upgrade to High Sierra. Every time I try, I just get an error message that says something like "installation preparation has failed, please try again later". I have no idea what the problem is.
Do you see any macOS installers in your Applications Folder?
If so and it is for macOS High Sierra, then open and use it to install macOS.
If so and they are for older versions, copy it to another drive or flash drive. delete them from your Applications Folder and try getting macOS High Sierra again.
Yes, I have the High Sierra installer in my Mac applications but it does not work. Every time I try the installer, when I get to the "restart now" part, it just keeps saying "an error occurred while preparing the installation. Please run this application again later"
I've never had any other user account on my computer. I'll have to try the Safe Mode thing.
I tried twice to boot in Safe Mode and install High Sierra, but it just keeps saying "an error occurred while preparing the installation. Please run this application again later"
Move the High Sierra installer to the trash and empty the trash.
Download a new High Sierra installer from the Mac App Store and use it.
2011 Mac Mini on OS Sierra won't update GarageBand, error message
