Hi there and welcome
For some reason your credit card company is rejecting the purchase, they may believe it is fraudulent and that someone has your card.
Contact your credit card company (tell me who they are if you need their details) and have them remove the block and you should then be able to process the purchase.
If you have continued problems, or would like any additional information or assistance, please do not hesitate to let me know.
Else if you can take a second to rate my service by clicking one of the stars at the top of the screen then submit, that would be greatly appreciated.