I was never able to register my UK Amex (British airways) credit card, which was the reason for using quickbooks orginally. Did anyone succeed in connecting it? Thanks!

Welcome to QuickBooks Community, alban-bress-gmai.

I understand that you want to link our bank accounts to QuickBooks Online. This feature allows us to easily download transactions, categorise, and reconcile the bank. 

In compliance with the Open Banking regulations, some banks may not be supported. For more information, please check Open Banking FAQs.

What I can suggest is to manually import the transactions. All you need is a CSV file from British Airways American Express that you can upload to QuickBooks Self-Employed. Please check these articles for the detailed steps:

• Manually import transactions into QuickBooks Self-Employed
• Understanding if you can connect your bank feeds to Open Banking

Keep on posting here if you need anything else. Take care!