Hello @Mario I
Thank you for reaching out on the community and telling us about your issue. There's a couple of things we might be able to try. First I would advise to check and see if there's potentially a hidden account that might still be connected. If you go up to tools -> Manage hidden accounts, see if there's any amex account listed that might still be connected. Could you by chance post a screenshot of the OSU when it say's there's an error with an account as well if the step above didn't work?
Once you get a chance just go ahead and post it here!
Thanks,
Quicken Francisco