I’ve just discovered a Connected Accounts issue, albeit an edge case:
You can only connect one credit card from a provider.
I’ve just tried connecting my rarely-used Barclaycard credit card - connected OK. I then tried connecting MrsW’s rarely-used Barclaycard and that connected OK too, but it took the place of my Barclaycard in the list of Connected Accounts. Connected mine again and it took the place of MrsW’s Barclaycard.
So it seems only one card from a provider can be displayed 