Can't download / install macOS High Sierra from app store - damaged error

Download macOS using Safari on your Mac

Safari uses these links to find the old installers in the App Store. After downloading from the App Store, the installer opens automatically.

• macOS Catalina 10.15 can upgrade Mojave, High Sierra, Sierra, El Capitan, Yosemite, Mavericks
• macOS Mojave 10.14 can upgrade High Sierra, Sierra, El Capitan, Yosemite, Mavericks, Mountain Lion
• macOS High Sierra 10.13 can upgrade Sierra, El Capitan, Yosemite, Mavericks, Mountain Lion

• Delete any previously downloaded installer.

• Empty the trash.

• Restart your Mac in Safe mode (hold down the shift-key at startup) and login to your user account.

• Download a fresh copy of High Sierra installer here:

https://itunes.apple.com/app/macos-high-sierra/id1246284741?mt=12

• Run the upgrade while still booted in Safe mode.

If the install is successful, the Mac should reboot normally.

Choose Applications from the Finder's Go menu, throw away the existing OS installer, and then download a fresh copy from the Mac App Store.

This issue isn't related to which web browser you use. The actual reason for specifying one is that Firefox doesn't properly handle the link; once the Mac App Store is open, it no longer matters which one you used. Chrome and iCab can be used as well as Safari.

(203008)

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...

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…

Check in Applications folder for " Install High Sierra " if one exists Drag and Drop to Trash and Empty Trash and try again.

Throw away that installer and using only Safari, download a fresh copy and try the install again.

Using an Browser other than Safari will present the error message every time or almost every time

Devil is in details Use ONLY SAFARI

Welcome and Thank you too :-))