Wife has her AMEX account, I have mine, both from before we were married. I manage everything in Quicken, including both credit cards.
Suddenly, her account wouldn't update with One Step Update, threw an 'Unable to Update' error.
So after all other accounts were OK, I did one step update on hers, all went fine, downloaded her transactions…which made MY AMEX account is now 'Unable to Download.'
Went back to do one step update, and I see that it lists BOTH accounts being updated, so when it throws to the AMEX site for login (something it only started doing within last year or less,) it only asks for ONE logon, which only applies to ONE of the AMEX accounts, and so the OTHER AMEX account is set to 'Unable To Update.'
I'm not sure where the bad programming is, at the Quicken end for assuming both accounts have the same login, or at AMEX, for not requiring a separate login for each account Quicken sends to AMEX for download.
But it's bad programming.