This copy of the Install macOS High Sierra application is damaged, and can‘t be used to install macOS.
That is the message I got when I tried to upgrade the OS from 10.12.X to High Sierra from the App Store.
Please help
Try again, deleting the old installer, restarting, then re-downloading and trying again with the installer found on the page here - How to get old versions of macOS - Apple Support
If you get a corrupted message...
Naw, not damaged, it's just that you have an old copy already in Applications, there are 2 cures...
If you're short of Data or Internet speed...Disconnect from the Internet & set the Date back to 2014, then you can run the Install MacsOS High Sierra App in Applications, so expired Certificates are not expired.
Or... trash the Install MacsOS High Sierra.app in Applications, empty trash & restart, then a new copy of a more recent version can be downloaded…
Thank you so much! That did the trick.
You're welcome!
Unable to upgrade to High Sierra
