Just received an email from support as well, confirming I need to wait two weeks.

If you attempted this method of payment multiple times with a failed result, there is a possibility of a longer block being placed on the account. This block can last 30 days. If you have done this, you will need to use a different billing method.
Thank you for contacting the SQUARE ENIX Support Center.
Only option is to get game time cards until it tides over. Which is doubly unreassuring because there's nothing preventing SE from declining the payments again in two weeks.

They should at least let me withdraw all the items and gil on my extra retainers....this is silly.