All resolved now.
I set this up as my client paying (but it was actually on my test card). A few workarounds happening at the moment while we wait for the full billing system to be rolled out and transition from annual payments in BC to SG system and rhythm.
To answer my own question - I logged in and updated the 'client' credit card to a new one, and the failed payment then was resolved when card with funds added as default, and attached to that product. ie. I did not need to do anything to trigger a new payment attempt.