Usually, it's one of two reasons:
1. We may not be able to ship to your state. Federal and state regulations restrict the states and counties where we're able to ship. Check out that list here.
2. Might be as simple as using a different credit card. Refresh the page or delete the cookies and cache from your browser, which may be blocking the new credit card information from going through.
Please contact us if you need further assistance with details on this request.