This is a similar issue to this closed topic, just a different map.
https://forums.garmin.com/forum/garmin-express/garmin-express-pc/1253046-garmin-express-there-was-an-error-installing-the-update
I have uninstalled and reinstalled Express. I have reset the watch. I have tried a Windows laptop. I have done all I can think of including deleting gupdate files like support chat suggested and still no joy!
ciq.forums.garmin.com/.../1347596.png