There are numerous reasons why a card withdrawal may not be processed:

• Some UK issued Mastercards do not provide "collection account" details. This means the issuer has not made available an underlying account for us to pay money back to.
• You are using a Mastercard issued outside of countries listed below.
• You are using a Mastercard issued within countries listed below but you are trying to withdraw more than what you deposited using that card.
• You are using a Mastercard BusinessCard where withdrawals are not permitted.
• You are using a Visa card issued in a country or from a creditor where withdrawals are not permitted.
• You have not met the requirements of the closed loop policy
  

Depending on which of the above applies to your account, you may be able to choose an alternate payment method to withdraw your funds; however you may be required to complete some security checks before being allowed to continue. If you are unsure, please contact Customer Service.
Please see further information about "Master Card Withdrawals"

List of Mastercard issued countries where withdrawals are accepted:

United Kingdom, Ireland, Andorra, Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, France, Germany, Gibraltar, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Luxembourg, Malta, Monaco, Norway, Romania, San Marino, Slovakia, Slovenia, Spain, Sweden, Switzerland and Turkey.