please post a screenshot of the flow trajectories. are you sure you have enough of them? if you plot a cutplot, does it show that you have flow in that area? if you use different faces for the flow trajectories, does it fill that area?
the best test is the cut plot test, if you have flow there, then flow trajectories should work. you probably just need to add more of them or move where they start from. sometimes you need to increase their length/time but only in extreme situations.