Have you made a purchase but have yet to receive a confirmation email or can't see the order in My tickets?
This could be an expired order, this happens due to either a technical failure, or the transaction took too long. Below is instructions to confirm this is the case however in most cases you will need to repurchase the ticket.
Sometimes this error appears due to the long waiting time on the payment page or an issue with the bank processing the payment. Your bank still may reserve the amount required for the order. This amount has now been released back to your account, but it may take up to 48 hours to appear as such.
You can check if your order has gone through by logging in and clicking on your name in the top right, then Profile, My Data, Orders. If the status of your order says "Expired" it means that the transaction did not complete and you should try again.