2020 MB Pro locked after Target Disk Mode

SOLVED! Somewhere in the past I MUST have set a Firmware password.....fortunately, the brute force method of hammering in EVERY possible combination of EVERY past iteration of secure passwords that I've EVER USED FINALLY found a match!!!!

This thread pointed me in the right direction:

If your Mac doesn't start up all the way - Apple Support

Now I'm gonna write that stinking password down somewhere that I will be SURE to remember it...like maybe a yellow sticky note on the screen.

Once I found the correct magic word, the computer entered Target Disk Mode exactly as expected.

Yeah, now that I have the Firmware password tattooed onto the meaty part of my left inner forearm, I should NEVER have this issue again!

Unfortunately, what I've got is a black screen with a grey padlock and a blank entry field for a password....I've had this 2020 MB Pro since new and DID NOT set a firmware password. I got stuck in this condition trying to go to Target Disk Mode. It will not accept the Admin password and I am the only user account. Tried PRAM reset, and SMC reset with no success. It will not get past this screen when trying to engage the Start Manager or when attempting to enter Recovery Mode.....

I'm truly stuck!