Trying to update High Sierra to Mojave, but the Mojave page on the App Store says the Mojave file is damaged and can't be downloaded. Is there anywhere else to get Mojave?

If there's a copy of the installer in the Applications folder or elsewhere on your computer, throw it away and go back to the Mojave page.

If it's referring to a copy on the server, click here and contact Apple.

(198033)

The Age of this computer will Govern what newer version of macOS it will Qualify to install. Use About this Mac from the Apple Icon on Desktop - the required Information will be there.

With the above information in-hand - follow this How to get old versions of macOS and verify what version this computer Qualifies to install. Make sure to use Only Safari to commence the download as Other may not work

Make a Time Machine Backup Before attempting. Notation - Mojave is the Last version to support 32 bit applications / extensions and Drivers. Catalina and Big Sur Only support 64 bit and there is not workaround.

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 Mohave App in Applications, so expired Certificates are not expired.

Or... trash the Install MacsOS Mojave.app in Applications, empty trash & restart, then a new copy of a more recent version can be downloaded..

The Time Travel - Back to the Future

:)

You're welcome, take care my friend! :)