Only part of an imported custom rig will animate

I’m attempting to import a custom character and rig into the engine. Both the mesh and skeleton seem to import with no problems, but when I import an animation (a simple walk cycle) and attempt to preview it on the existing skeleton only the arms animate, while the rest of the mesh is stuck in the first/last pose (I don’t know which one it’s stuck on, because it’s a cycle).

I would appreciate some insight into what might have gone wrong during rigging, export or import. Thanks!

Well, the animations need to be designed for the skeleton, if not, you’ll get this sort of problem
Otherwise you need to ensure the skeleton used for the animations and your custom rig actually match both in structure and naming of all the bones etc.

The animations were built with the custom rig in maya, and all the bones are named appropriately.

Did you import it onto the correct skeleton in the popup window? How complex is the rig and are you getting any errors on import?