Thanks folks - I won't even try to give up Sci-Fi - it's my choice for my big birthday meal and my top priority for the day (haven't been there in almost 30 years and my spouse and kids have never been).
I had an AM Hollywood and Vine Reservation as well (leftover from before I was able to book Sci-Fi) so I tried to drop that and pick it up as a Fantasmic Dining package- also didn't work.
That being said, when I went to rebook it, there were a ton of H&V reservations open throughout the day so if you were just wanting to book there, now is a good time to do it!