Thank you for taking the time to visit the Community to report this issue although, I apologize that you have not received a response.
When you perform a One Step Update in Quicken you may receive an error CC-555. This error indicates there is a connection issue between Quicken and your financial institution.
This error message will be presented when the financial institution is blocking access to their servers, preventing Quicken from retrieving data to download to your file.
I do not have any details to provide on if the block is permanent or temporary. Several financial institutions have been periodically blocking traffic due to Covid relief payments.
I would recommend attempting to update every 48 hours to see if the block has been removed. I would also recommend contacting American Express and asking to speak to a supervisor to confirm that they are no longer supporting Quicken.
I hope this helps.