Invalid Payment method annoyances

So recently I’ve been using the same card to pay for things on iPhone, I had issues once but fixed it but recently today it started saying invalid payment method or declined card. I’ve looked up the way to “fix” it here but it doesn’t work at all. All the information is correct and it has plenty of funds to pay for the item. I logged in and out of my iPhone as well to see if it works, it did not, all it says is “unable to process” has anyone else had this issue or know anyway to fix this??