pm sent:

Upon further examination, I think the account/profile is not corrupted - rather the Sign In block/module is not communicating with the DB correctly. Interestingly, it works fine on mobile. So this really looks like a server side problem in the block that serves Log In function on Desktop only.

Edit to Add: since I was using a different account to test from mobile and that worked - I incorrectly assumed the problem with user-based. In fact it appears to be desktop vs mobile.