I have attempted purchasing a plan four times with the same error message:
We are unable to approve your transaction at this time.
There are a number of reasons for order failure, among them errors in the payment information, or billing address, or an inaccurate email address. If you have verified your information and are still unable to place your order, please contact Customer Service and order by phone. Call 0800 007031.
all four times, money was taken out of my account, but not approved on CC side.
Contacted support and was told to create a new ID and try again, and same result.