My card was declined, but I know I have the money.

This usually happens for a very simple reason: The billing address.

The fix: Make sure the address you type into the "Billing" section is the exact one where your bank sends your monthly statements. If you moved recently, the bank might still be looking for your old address.

If the address is correct, this is likely your bank declining the charge until they hear from you to confirm. Call your bank for next steps.