I finally contacted EDF via Facebook, not one of my favourite channels of communication, but there we go.
I had an online chat in French with a very helpful person, who looked at my account. The problem was I had not updated the SEPA. I explained I had not been notified, but I was willing to do so. She asked me for my account details, sent me a code to quote back to her, and then she made sure my EDF account would function, staying online until I confirmed it.
Bingo. I can once again monitor and check my account.
Gina JOLLIFFE, Creuse