/sbin/mount -uw /

macOS 10.15 or later. >>>.  mount -uw /System/Volumes/Data

Execute the following commands:

cd /var/db/

rm ./auth.db

rm ./auth.db-shm

rm ./auth.db-wal

Restart the computer by executing the following command

shutdown -r now

Hi MrSuaz, since we cannot log into a user account, and safe mode does not work either (we tried logging in but we get the same black screen) you mean we should try to run this in a terminal while in recovery mode, right? (We did make sure the volume was mounted before attempting to find the files we were supposed to delete)

One thing i am not fully understanding is this:

/sbin/mount -uw /

macOS 10.15 or later. >>>.  mount -uw /System/Volumes/Data

What does this refer to? can you elaborate a bit on this? Thanks!

The original fix does work, but the key is mounting the correct volume. Here are the steps for the helpdesk:

-Boot into Recovery Mode
-Choose Options>Continue
-Select User, click Next, and enter password
-Go to Disk Utility>Continue
-Expand Macintosh HD volumes
-Click on Macintosh HD - Data
-Click on Mount in top-right corner and enter password

Macintosh HD - Data should now have the Unmount button in the top-right corner, indicating it's been mounted

-From top-left corner, Quit Disk Utility
-Go to Utilities>Terminal
-Type "cd /Volumes/Macintosh\\ HD/var/db/"
-Type one by one and press Enter:
rm ./auth.db
rm ./auth.db-shm
rm ./auth.db-wal

There should be no errors if commands ran successfully.

-Type "shutdown -r now" to reboot.
-Log in normally at first Mac login screen - the second login screen should now be gone.

If you run "/usr/local/bin/authchanger -reset -jamfconnect", which you should be doing anyway as a daily policy so everyone is authenticating via Jamf Connect, it will undo the settings and break it again. The permanent fix is to update Jamf Connect to v2.28. Confirm this version is installed on the Mac and you should be able to log in normally via Jamf Connect after a reboot.