Hello, thank you for reaching out to Microsoft Q&A.
Recent security changes prompt appear if any modifications are detected to your TPM memory, which can trigger a reset of your PIN on the Windows sign-in screen. This may have occurred if you recently installed BIOS or Windows updates.
May I please confirm whether you previously set up Microsoft Authenticator verification on your mobile device? Also, did you recently change or reset your phone, which may have removed the Authenticator app?
If you no longer have access to the Microsoft Authenticator app or the phone number used for verification, on the Verify your identity screen, select I don’t have any of these and follow the prompts to replace your security information.
Note: If you remove all of your previous security information and replace it with new information, your account will be placed in a restricted state for 30 days.
During this 30-day period, you will not be able to reset your PIN. If you need to use your device during this time, you will have to perform a complete factory reset from the Windows Recovery Environment, which will erase all data on the hard drive.