Monterey Upgrade
Downloaded Monterey upgrade.
Have my latest Big Sur installed on my MacBook Pro Retina Mid 2015.
The upgrade preparation runs for +/- 1 hour, after which MacBook reboots.
After reboot, instead of upgrading, my MacBook return to Big Sur login screen.
Tried 5 times, after which I tried also secure restart, but nothing helps.
Monterey simple won't upgrade ...