I feel your pain, I signed up for the Bday promo as well and need to call the skymiles office on Monday.
I registered for the promo and then booked my flight TPA-LAX-NRT-SIN/SIN-ATL-TPA within hours of signing up for the promo. I did get the email from DL.
So this week I checked my account and found a 9m Birthday entry with 1089 miles. So now I need to go fight with a phone agent about why they did not give me my 20k+ miles that I am owed.
It stated I needed to signup & book by March 31st and then fly by april 30th. So I did not sign up till I booked the trip as I did not want one of my shorter trips to use the promo. And it States it needs to be a round trip.
So between the date I signed up and flew to SIN and back I did not take any Round Trips on DL. I did do a couple one way trips, so based on the wording of the offer my SIN trip was the one that should be the promo trip. The SIN trip was only taken as a MR because of the Double EQM and Birthday Promo, so they better give me my bonus miles.