I attempted several times to use the "Sign In Options" yesterday without success.
I also noticed that in Settings where it usually said - Accounts - and my name, MSA and Administrator,
It said "Local Account Administrator!" instead.
THis morning after I booted I got offered "Set Pin" and that worked normally.
I have never seen the phrase Local Account Administrator before.
DISM and SFC showed no problems today so perhaps things have corrected themselves..??
Davy.