Payment doesn't go through
This situation is common if you have a non-US credit card and you don't often make purchases out of your home country.
Usually this is because your bank is trying to protect you from fraud. Trying a different card might help as well. Generally speaking, credit cards have a higher success rate than prepaid cards.
If nothing works out, the last resort is to call your bank and explain the situation. The bank should be able to let the transaction through.