Purchase history and payment method

I recently tried to update an app which lead me to the verification page however when I try to update my payment method it responds saying that the payment method is invalid. I looked it up a little and found that this could be because of pending purchases in the purchase history so I checked and I found one however I don't know how to remove it from pending or pay for it. The payment method I previously had has enough money in the account to pay and all the details are correct so how do I complete the payment for that product? And after I do, will my payment method stop being invalid? Or do I still have to change it?