The add-on to add omaha to a holdem version costs $54.99. Your discount should be 40% of the purchase price of PTO (< 1 year), which I think will be .4 * 55 = $22. So you should pay $32.99 if I've done my maths right.
If you go to the purchase page and Add To Cart it should show your discount. If not, you need to link your products on My Account -> My Orders. If you're not shown the discount you expect please create a tic and we'll sort you out that way.