Have you checked with your bank whether the transaction was successful? Call the card centre. Do you have any reference/transaction reference number? Remember it is last day today!
If in doubt, call the bank and/or Legoland.
Write to them, so that there is evidence you tried to buy the tickets but are not sure whether the transaction was completed. This way, you MAY be able to buy tickets in the future at the discounted price if the transaction today was unsuccessful.