Hello Robert, welcome to the Microsoft community, I'll be happy to help you today;
I understand that you are having problems with the challenge phrase on the Windows 10 login screen;
I already had this problem myself and fixed it by following the instructions in the video below:
https://www.youtube.com/watch?v=tKKLqXBkYCk
Disclaimer: There are links to non-Microsoft sites. The pages appear to provide accurate and secure information. Watch out for ads on websites that may advertise products that are often classified as PUPs (Potentially Unwanted Goods). Thoroughly research any product advertised on the websites before deciding to download and install it.
Hope it works, see you soon!