Hi phil Moor,
Welcome to Microsoft Community.
Based on the original description, the device seems to be experiencing issues related to the Windows Hello.
The reason you are currently experiencing issues may be related to the motherboard replacement, a hardware change process that alters the state of the data in the TPM module, which in turn affects the state of the data related to the Windows Hello service and the verification process at the software level.
What is TPM? - Microsoft Support

If possible, you can try resetting the PIN in the Microsoft account dashboard first to minimize the influence.
How to sign out of your Microsoft account everywhere - Microsoft Support


If you are currently in a locked screen and unable to log into the Windows desktop environment, you may need to refer to the product manual or visit the device manufacturer's website for the steps to reset the TPM module. Or you may need to refer to special thoughts shared by other community members.
The content in the following thread described examples shared by other community members.
my windows 10 is pin locked - Microsoft Community

| Disclaimer: Microsoft provides no assurances and/or warranties, implied or otherwise, and is not responsible for the information you receive from the third-party linked sites or any support related to technology. <br><br>If you are going to modify BIOS Settings, please back up all your personal files first to ensure you do not lose data. |
If I misunderstand your situation, feel free to correct me and share the information.
Best Regards,
Kyo.Y - MSFT | Microsoft Community Technical Support