This happens when with a BIOS upgrade, I had that happen a few times. You should be able to log in with your Microsoft account. and setup a new PIN. You need to make sure you are online for this to work.

I have made a local system account for myself just to avoid this issue.

Thanks for your suggestion, Vanadiel.  I understand what I need to do, but, unfortunately, I have no way to select any other login option.  The supplied "Set Up My Pin" option fails as described and I don't have a prompt for 'Sign-in Options' that would allow me to enter my MS account details.

Steve

Look below the PIN text box. 

• If you see I forgot my PIN, select it and follow the instructions to reset your PIN. If there are multiple accounts on the device, choose the one you need to reset.

• If you don't see I forgot my PIN, select Sign-in options and then select Enter your password.

Thank again, Vanadiel, but as I mentioned above, I only have the "Set up my PIN" option, which doesn't work.  I don't have the "I forgot my PIN" option, nor do I have the 'Sign-in options" prompt.

---

@SteveTetch2 wrote:

I fired off the upgrade, watched the system restart, then left the room for a while.

When I got back, the normal start screen was there with date and time and the same the Microsoft "rocky cave at the beach" picture. I clicked with the mouse to bring up the PIN prompt and saw this message: "Your PIN is no longer available due to a change in the security settings on this device. Click to set up your PIN again.".

---

Something similar happened to us once (while the Aurora-R6 was still fairly new).

https://www.dell.com/community/Alienware-Desktops/My-Aurora-R6-The-Adventure-Continues/td-p/6063705

It was only that once. Machine uses Local Account with Dell Factory software-load.

I figured it was either a Windows-10 glitch or more likely, the way Dell provisions these machines.

I've never really trusted Microsoft's "Roll-back" feature. And if PC is Posting, Back-Flashing your BIOS is usually a bad idea (due to version dependencies). Finally, I've know of people getting locked-out of their machines, jacking-around with their Logins (while machine is acting up).

In your case, if I didn't have a current Macrium Reflect Full-System Image, I would create one. If I did, I would run a Differential real quick to catch-up.

Then, I would trying going FORWARD with fixes (not backwards).

And if that does not work, try the safe boot mode: Windows PIN issues 

I have recovered from this in the past, but I remember one time the Windows Live service was experiencing login issues and I could not log into my Microsoft Account. Ever since then I made sure I always have a local account as a backup, because if your internet connection goes down, your Windows login/PIN will not work either.

You could try CTRL-ALT-DELETE at the login screen, see if the popup menu will let you change users.

If it does, you can try your Microsoft account login that should be linked to your original PIN.

I had no luck going back to BIOS 2.1.3 from 2.2.1 when that update broke my machine. Tried all the options. There are some BIOS versions that cannot be downgraded from. It says for Security Reasons. 
2.2.4 was not available to me at the time, but 2.2.2 also failed to solve the issue. Motherboard replacement was the only fix.

The suggestion from Dell tech support via private message is to downgrade the BIOS.  They've included a link to the correct download page, but the knowlegebase article that describes the downgrade process includes many cautions and caveats about the whole process.  I'll confirm that's the only available option before I do anything.

I have to say that I'm somewhat annoyed at the fragility of a system that can be buggered (technical term) so easily in this way simply by applying a BIOS update that was recommended by the manufacturer's own maintenance application, which also managed the installation of the update!

I haven't faced this issue on any other manufacturer's PCs I've used in over 30 years.

It's actually a Microsoft thing. They want to make sure that for security reasons you cannot move a drive over from one system to another with the same PIN.

The BIOS update will reset some information that leads the OS to believe it's connected to a different motherboard, and requires a new PIN.

I agree it is highly annoying, and the reason why it is a good idea to always create a local Administrator account so you can log into windows with a regular user name and password as opposed to a PIN or any online only login options.

I am not sure why it does not allow you to log in with your Microsoft Account. Maybe it's something with the Windows Home version.

That's why when initially setting up Windows disconnect the internet and go for a local account!

I would suggest to add a local account to windows, for any future recovery, as this will likely happen again should you update the bios in the future.

Local Windows 10 Account Creation