user profile service service failed the sign-in

@OldGuyFromCdn
- that starts with enabling the built-in admin account (done above) - but user cannot log in to any account even that one.

*** considering, for example, the suggestion there

NTUSER.DAT file stores data about the user account, and if it is corrupt, you must replace this file.

- you can do that without being able to log in. To do that you need to edit the registry offline.
One way to do that is to create the (free) Kaspersky boot disk which includes an offline registry editor

Kaspersky Rescue Disk Review (A Free Bootable AV Tool)
or see:
Regedit as offline Registry editor – 4sysops

This may or may not help in your situation.

What you described is the lock screen- the problem being that having dismissed it you don't see a normal login screen.

My view:
If no part of the user profile service tutorial I cited above is available to you, and you can't exactly and precisely reverse whatever you did by editing the registry offline then, since you have not chosen to protect yourself using disk imaging (as is endlessly recommended here) then

- ensure you have a full backup of all personal data (I hope you have most backed up)
- include any program license keys, consider browser favourites, any email client's data

and clean install.

Attempting to recover the several accounts you have using that tutorial does not seem a good way forward, even if it were possible to start on that.

When you clean install, start using 3rd party disk imaging as early as you can and throughout the installation and configuration process. Naive users will try to configure everything, then create their first image.