You must assign a client to each seat. Please follow the instructions on the pricing page and try again. There are errors on the page Adult/Senior tickets must be purchased with Juniors in the Family Area in Blocks 137,138,139 and 140, a maximum of 4 Juniors maybe purchased per Adult/Senior ticket I am a season ticket holder buying 3 additional tickets for non ST holders. WTF does 'assign a client' mean?
This shouldn't apply to your situation, but assign a client is when you use additional ST Passess to buy more tickets. I've already done this. It should automatically assign your tickets to your own card.