How do I log in with my Admin account after upgrading to Monterey?

I suspect the corruptions have not been completely cleared.

There can be various causes, such as changing short names, or storage corruptions, or hardware failures.

Only reasonable means to clear it is a re-installation, and using Setup Assistant or Migration Assistant to reload the users’ files and data.

What did Apple have you do?

Hey Kuzie17!

Is there another admin account you can login to to make any necessary changes?

If not, and safe boot/First Aid doesn’t allow login either, you may be able to create a new admin account to make those changes while in recovery mode. (This process will depend on your Mac model, year and OS version),

Another option still available is to reset user permissions from recovery mode if needed. This process can still be done while in recovery mode, and requires another reinstall of the OS.

Mind you, any of these changes would require an admin password to do if your disk is locked, but sounds like you already have the password.

Another important question, do you have your data backed up? (Just in case it’s an all or nothing real)?

Let me know and I’ll help if I’m able to!

Kuzie17 wrote:

Check disk utility for error, run terminal code, safe mode

Which means little in this case, alas.

What did Apple tell you to do, and have you work through to get your main login working?

Because this Mac seems a candidate for backup and reinstallation.

So far, all of what you're describing reeks of a systemic corruption, though the triggers are open-ended.

I'll assume you have complete and current backups of this Mac. If not, go get those configured and going.

Boot into Safe Mode and try again.

How to use safe mode on your Mac - Apple Support

That can avoid some issues, but there are various sorts of corruptions that can involve reloading and migrating to resolve.