Hi R Dore
If the device was reset using Keep my files, Windows may still be linked to the Microsoft account that was previously configured on the PC. At the sign-in screen, please check whether you can select Sign-in options and use the Microsoft account password (not the PIN). Also verify that the laptop is connected to the internet from the lock screen, as a recently changed Microsoft account password may need to be synchronized with the device.
If the password is still not accepted and the PIN reset option is unresponsive, try booting into Safe Mode with Networking and test password sign-in there. If you are able to sign in, you can recreate the Windows Hello PIN afterward.
Can you confirm whether the account shown on the sign-in screen is a Microsoft account (email address displayed) or a local account?