IMac reboots in Big Sur instead of newly installed Ventura
I have a 2019 iMac running Big Sur. I have tried to download and install Monterey and Ventura (separate tries) and both upgrades fail. the new OS will download but the install process seems to get cut short and the computer restarts back in Big Sur. I have already confirmed that there is plenty of space on my hard drive for the install (almost 1 gig free). Any ideas on how I can get the computer to update its OS to Monterey or later ( I want to use universal control because I have two Macs sitting side by side). Help please.
iMac, macOS 10.12