updating Mojave to catalina

Third-party Anti-Virus, Cleaning, Optimizing, Protecting software and VPN's can cause problems when trying to update the macOS.

If you have any of those, uninstall them as per the developers direction,

then follow the steps at > Update macOS on Mac - Apple Support

Then if you still get the error message, try updating in Safe mode

as per > If an error occurred while updating or installing macOS - Apple Support

Also keep in mind that Catalina is now out-dated and you could be forced into updating to one of the later supported macOS version like Monterey, Ventura or Sonoma.

subramaniam226 wrote:

I installed sonoma by starting the iMac with option+commnd+R. This allowed me update it directly from mojove to sonoma.

Thank you for your help.

Glad to hear that you were able to upgrade the macOS.

You're welcome.

[ redacted ... /viking]