Object hierarchy ignored in animation

I’ve FBX imported the pieces of my aircraft model into Unreal and rebuilt its hierarchy successfully within the program. This “build” hierarchy consists of individual components of the aircraft that will animate independently while attached to the main aircraft.

In other 3D animation programs, I’ve usually attached such a “build hierarchy” as a child to another “motion hierarchy” using nulls or locators to represent pitch, roll, yaw, etc. This helps to isolate motions, minimize unwanted key framing and mostly avoid the gimble lock of overlapping axis.

The “build hierarchy” in Unreal works perfectly. Using basic sphere objects in unreal I build my “motion hierarchy” with Master on top and the pitch, roll and yaw sphere objects parented to it accordingly. When I test their relationship they work as expected. But when I attach my “build hierarchy” to the very bottom of this family it fails to respond as expected. I rotate the master, his children come along for the ride but my aircraft does not move.
The outliner shows the descending relationship. If I close the arrow they all fold up under the Master as expected. If I turn off the eye of the Master everyone in the family, including my build assembly disappear. It all looks as if it should work.

I’ve done various tests, simplifying the hierarchy and still nothing. What am I missing and is this even possible to do in Unreal?

Thanks for reading all that.