So Restricted Software got mentioned, but the message "The requested version of macOS is not available" doesn't sound like a Restricted Software thing. (The solution to undoing a legit Restricted Software record, by the way, is to run sudo jamf manage after un-scoping yourself)
To me, that message sounds more like the update is potentially being blocked by the software update catalog itself. Try running this via Terminal on the computer giving you the problem: sudo softwareupdate --ignore
In the returned output, does it list macOS? If so, run sudo softwareupdate --reset-ignored to clear that out. Then give it another shot. You might need to reboot after doing that, but I don't think so.