The most common cause is the lack of money on your account or incorrect personal details.
In that case you can contact your bank from which the card was issued.

Below you will find information which might be the cause of the canceled transaction:
not enough amount of money on your credit card,
the card is reported as stolen or conditioned,
incomplete or incorrect personal details,
missing CVC/CVV2 code,
an attempt to pay with Maestro – right now we do not have the ability to make payments when using Maestro card,
an attempt to pay with Visa Electron– right now we do not have the ability to make payments when using Visa Electron card.

You can pay with this cards which were issued by Millenium Bank, DB-PBC, Inteligo