If you still didn't understand the whole word "recurring" dumbing it down it means the only method you can buy membership is doing a pay by monthly contract for example when your first month runs out, it will then automatically take the money you have out your account and add another months membership to your account. Without you having to do anything but supply the money. So if a prepaid card only has "$5" on and you buy one month then leaving you with "$0" when that runs out, when the next month comes around it will try and renew (buy another month) costing "$5" however, your balance on your card will be "$0" so the payment cannot be made, because of this the card is not allowed to be used for membership just like how in life you can't use a bank cash card for payment's like this (paypal won't allow cash cards or as my bank said anyhow), however you can use debit/credit cards because your bank will allow an overdraft with a % back when you get money in your bank. This is why that works.
Just thought i'd try make it understandable as it might be a while before kenny replies. But RK is truly right, and tbh never thought about that before but all makes sense now lol. Not quite sure how you don't understand after two people saying the same thing though, your best bet is just get a debit card from your bank if you have one (depending on your age ofcourse depends what you can open).