the update could not be verified

Hello, RonCambridge.

Thank you for using Apple Support Communities.

I understand you're unable to install macOS Catalina because it can't be verified. I'd like to help. First, try deleting the installer and then restart your Mac. This can sometimes help resolve issues.

Then check to make sure your Date & Time are set correctly.

Have you recently installed any RAM?

Run Disk Utility and check your hard drive: Repair a storage device in Disk Utility on Mac

If possible, try connecting to another Wi-Fi network.

Keep me updated if any of these steps help.

Cheers!