I have been making it for about 2 months on and off now and never had a problem with it not riseing. I used yellow cake mix and Angel Food made it for a girl friend of mine with fresh strawberries on top she loved it. I gave her some to take home to make for her granddaughter she sits for her alot she is going to call it the Magic Cake. LoL I want to try my next batch with Lemon cake that just sounds so good.
As for your problem maybe your mix settled try mixing it up again and see what happens.