Mini (M1, 2020) can't upgrade to Monterey 12.4?

Third party AVware, Cleaners, Optimizers, VPNs and other junkware can block macOS updates. If you have installed any of those, uninstall them as per the developers instructions and then try to update.

If that doesn’t help, startup in Safe Mode and then see if the macOS will update.

see > Start up your Mac in safe mode - Apple Support

Good and thank you for the updated info.

Terminal command again and this time as per below

software-update --fetch-full-installer --full-installer-version 12.4

The Above will pull the Full Version of Monterey 12.4 and place a new Application in the Applications Folder.

It will be called " Install Monterey.

It will Not Auto Launch

Would suggest

1 - Disconnect all external Drives

2 - Restart in Safe Mode. This will perform a Disk Repair, clear cache files and only load Apple Software, extensions and fonts. The boot up will be slow and can take some time - Normal.

3 - Once Logged into the computer - Now Launch the 12.4 Installer

4 - Why Safe Mode > Find it can be more effective

What are the results of the below Terminal command ?

softwareupdate --list-full-installers

You’re welcome.

Good work.

Am late to the game here ☺️

Thanks for the terminal tid-bit.