We appreciate that when a payment is declined it can be frustrating. You may well know you have sufficient funds in your account to cover the transaction, which makes it all the more annoying.
When a payment fails we are never told the reason why by the card issuer. Just like when you might go into a physical store we see either Approved or Declined.
In this case your card was declined. There could be many reasons behind this, including and most usual the card issuers anti-fraud department who for some reason have flagged the transaction as potentially risky.
We would recommend that you contact your card issuer about this as there is nothing we are able to do to force a transaction through.