Unable to update Billing information

After cancelling my Direct Debit payment method, with a view to update to Credit Card - on the recommendation of Zwift Support to get my Elite promo code to work - I am now locked out of using Zwift. The Billing screen is blank and despite sending four Support requests over the last 5 days, I’ve heard nothing. To make matters worse, my bank account was debited last week so I have another 3 week’s Zwift credit. Has anyone else had this and is there a solution? Desperate…