Just upgraded to FFv3.5.2. Never noticed a problem before so decided to try it out...
From the splash (home) page I can enter OP# and PIN in the OnePass Sign In area, hit enter and all loads OK
BUT
If I click Sign In on the header (up there just to the left of lovely Alex) and get the page with fields to enter OP# and PIN, when I enter that info and
- hit Enter - blank page reloads
- click Sign In (Secure) all loads fine