Can't sign-in after 20H2 update

Hi Adam. I'm Greg, an installation specialist, 10 years awarded Windows MVP, and Volunteer Moderator, here to help you.

I'll give you what works best for sign-in problems which I've helped people here fix daily for five years. Often this is caused by a corrupted account. It previously required a Reset or Reinstall but if necessary I'll show you a way to swap in a new account to replace the old one while saving your files and apps.

You can try to change your MS Account password online then assure you're connected to internet at the sign in screen from Network icon in corner:
https://support.microsoft.com/en-us/help/402683...

You can try to change a Local Account password from the sign-in screen if you set this up in advance:
https://support.microsoft.com/en-us/help/402845...

If not then enable the built-in Hidden Administrator used for emergencies from the Sign-In screen to sign into to create a new replacement account:
https://www.isumsoft.com/it/enable-hidden-admin...

These steps require bootable media which is the only repair method that doesn't require a password. If you can't or don't want to create bootable media, you can first try to Reset Windows from the password screen as shown here:

https://www.youtube.com/watch?v=Zonjyd2L_GQ

To create Windows 10 Installation Media on another PC install Media Creation Tool and follow the directions here: http://windows.microsoft.com/en-us/windows-10/m.... Uncheck the box for Recommended Settings to choose the exact version and bit rate for the target PC only.

Insert media, boot it by powering up PC while pressing the BIOS Boot Menu Key given here: https://www.sysnative.com/forums/hardware-tutor...

If the media won't boot you may need to enter BIOS/UEFI Setup (pressing key given in chart in link above) to turn off Fast Boot or Fast Startup first.

Choose the boot device as a UEFI device if offered, on second screen choose Repair Your Computer, then Advanced Troubleshoot Options, then Command Prompt to enable the built in Hidden Adminisrator:
https://www.isumsoft.com/it/enable-hidden-admin... Sign into this Administrator account by leaving password box blank.

Then create a new Local Admin account to replace yours:
https://www.isumsoft.com/windows-10/3-ways-to-c..., sign into the new account, test it works OK, move your files over at C:\Users

You can try to repair the old Account by running a Repair Install: by installing the Media Creation Tool from this link http://windows.microsoft.com/en-us/windows-10/m... Choose Download Tool Now, Install the tool, open it and choose Upgrade this PC Now. This reinstalls WIndows while saving your files and apps in place; takes about an hour, resolves most problems. It also brings it to the latest version by the most stable method.

You can also delete the old account by one of these methods:
https://www.tenforums.com/tutorials/5464-delete...

You can then if desired change it to a MS Account: https://www.tenforums.com/tutorials/5375-switch...

If that fails go back to Troubleshoot Options to try a Reset, saving files if needed.

And if that fails choose Install Now, then Custom Install, then at the drive selection screen delete all partitions down to Unallocated Space to get it cleanest, click Next to let it create needed partitions and start install - this makes it foolproof.

Everything needed to get the best possible Clean Install is here: http://answers.microsoft.com/en-us/windows/wiki.... It is a better install than any amount of money can buy and a great learning experience that will make you the master of your PC because you will learn what works best and how to apply it with your own hands.

If you have files that aren't backed up you can use the same bootable media to try to rescue your files using these methods: http://answers.microsoft.com/en-us/windows/wiki...

I hope this helps. Feel free to ask back any questions and keep me posted. If you will wait to choose if I solved your problem, I will keep working with you until it's resolved.

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