I can’t add my debit card on my iPhone and I don’t have any unpaid balances. So idk what to do can you please help me?

I’ve been trying to add my debit card all day and every time I try to add it suddenly it says that it’s declined but all my information is right. Then I looked around online to see if I could find more information about it so I looked threw my purchases and I don’t have any unpaid balances or anything so I don’t know what to do.