Hi Cindy Shay,
Since the usual PIN-reset steps have already been covered by AI answer, so you can follow to proceed. Please also check that the PC is connected to the Internet from the sign-in screen, then restart it and try the PIN setup again. Windows Hello may need to verify your Microsoft account before a new PIN can be created.
If it still fails, please let us know what happens when you try to set the PIN, including any exact error message or code shown. That will help narrow down the next step.