‘None’ payment option won’t work.

For a long time, I wasn’t able to download anything because my payment method (a prepaid debit card) was declined and I had no other way of payment. Now, (finally) I have the option of having no payment method but when I save it, it keeps telling me it’s invalid.

I still can’t change my payment method because I don’t have any other way of payment. If anyone could, please help! Any type of help is appreciated!