Password Field Obscured in Norton Login on Firefox

When I login to Nortons on Firefox, the password field is obscured. Initially it was partially obscured and I could see half a cursor and type in the password but now after 3 years I can't see it at all so can't login. It is fine in Chrome.

I am on a HP laptop running Windows 10 64bit.

I was assuming it was a display issue in Firefox but can't find anything to explain it.

Has anyone experience this before?

Thanks