If you are having difficulty placing an order using a debit or credit card then the likely explanation is that your card does not have its CBP (Cross Border Payment) feature activated.  This is quite normal and most card issuers do not activate this feature by default.

The resolution is very simple.  You should contact your card issuer and explain that you are attempting to place and overseas order an require CBP activating.  Once this is completed (it takes around 2 mins to resolve) the payment should go through without issue.