Amazon Checkout Issue Won't Accept My Card Balance

I have been experiencing a problem trying to place an order on Amazon US and I would like this to be resolved as soon as possible. I am trying to buy a doll and a DVD, but I cannot complete the checkout process even though I follow all the steps correctly. I first tried to place this order last night and have tried several times again today. I reach the checkout page, apply my available card balance, but the “Continue” button does not light up or activate, so I am unable to proceed to complete the purchase. I have successfully placed orders on Amazon before with this same account and payment method, so this appears to be a new technical or account-related issue. I request that you urgently check my account and the checkout process, identify what is blocking the order, and fix this problem so that I can place this specific order as soon as possible. I would appreciate a prompt response and a clear explanation of the cause once it is resolved.