DoN's 3D Pathfinding for Flying A.I. [Support Thread]

At the bottom of TickScheduledPathfindingTasks you will find CompleteNavigationTask(i);. Inside that the ResultHandler delegate is what notifies the FlyTo task that it can begin routing locomotion to your pawn. If that delegate worked, it should invoke UBTTask_FlyTo::Pathfinding_OnFinish function inside BTTask_FlyTo.cpp.

I’d take a step back and compare your setup with the sample project first though; behavior trees, pawns, manager setup, everything. This kind of low-level issue hasn’t been reported before so might be easier to first run your usecases in the sample project first and then migrate them out to yours.