Hi Keith Britten! i also baked some cakes but i guess you must choose the cake flour cause if you use the all-purpose-flour you have to put still a baking powder or sometimes yeast so it will rise .... That's all i can think about your problem .... And about the syrup im not familiar in Davao so i can't help you there hehehe
Goodluck in your cake hope it will rise soon hehehehe