valrizzo wrote:
it also says that version of the install is damaged and cannot be used!
Not the first time someone has encountered this message. The installer isn't actually damaged; what happened is the certificate associated with the installer had expired (possibly the installer was downloaded some time ago).
The solution is to change the date on your Mac back to when the version of macOS you are trying to install was current. Go to System Preferences > Date & Time. Disable (uncheck) "Set date and time automatically" and then manually change the date. For High Sierra 10.13.6, I'd suggest October 1, 2018. Then run the High Sierra installer. After the upgrade is complete, reset the Date & Time to automatic.
UPDATE
After I first saved the above, I saw your message that you successfully upgraded to High Sierra by downloading a new copy of the installer. Great news! (So, you can ignore my message ...)