Look what I've got while updating maps on my brand new Fenix 6 Pro (I'm on a Mac OS 2020):
Really ??? And this is a 700+ euros watch ? Are you serious?
Garmin has some really hyperbolic customers.
And you let them buy a 700+ euros watch? Are you serious?
I'm a bit frustrated after 3 hours of download retries, all failed with some generic errors.Then during the last retry I got this with 997.3% completion and -2147483648 remaining minutes... Well, I think I'll stay with the current maps for the moment.
Delete Garmin Express. Download and install a fresh version.
FWIW I'm running MacOS 11.0 Beta on my MacBook Pro and my wife has MacOS 10.x on her iMac. Neither of us are seeing any problems.