MacOS – “Item not available” error when trying to upgrade to High Sierra

Depending on when you downloaded the installer precisely, this answer may provide a clearer reason for the issue.

• I have noticed that their have been one or two system updates for macOS High Sierra in the past weeks. The fact that you are encountering this issue is most likely due to the fact that your version is older than the currently available and up-to-date one in the Mac App Store today.

• Please try downloading the latest version.

Then let me know how you get on with the install. This would be the only logical reason for it not working on a supported / compatible system.

The most likely error is that the disk isn't partitioned correctly. If you have a bootable installer or can connect it in target disk mode - try erasing the entire physical volume again.

In the image above - you want the top item selected and not the volume under the physical drive. I like to click erase and then not make any changes from the defaults - leave the name Untitled or whatever the default name is - not Macintosh HD.

Then when the installer runs, you might need to look at the install log (press command 3 and command L when the install starts) or we'll need to chase down where or if your installer is saved to disk after the install aborted.

In some newer hardware - you need to be connected to the internet with no firewalls so the installer can go get the components for the hardware - perhaps that step is failing and the install log would likely show that.

Here is Apple's full steps on the erase - so choose it over my steps above if mine fail you.

• https://support.apple.com/en-us/HT204904