Automatic payment details not saved

Mr_MELT

So each month a few customers get an automatic recurring invoice from me. Most pay by standing order, but one likes to use a credit card to pay. Each month he clicks the checkbox that asks if he wants to save his details to enable automatic payments, but still I cannot take automatic payments from him and it's beginning to annoy him.

I use Stripe as the payment gateway integrated with Wave. I can't understand why its not working as I thought it should.