Missing modeling parts in Unreal 4

I exported a rig from Maya, and some parts of modeling is missing in unreal,
Don’t know if it’s simply invisible or really gone.
And somehow I found out that missing parts are not skinned to a skeleton, I think they are simply parented to a locator or something. I bought a rig for my personal work so not knowing about the details of it :blush:
Well, if two kinds of meshes(Skinned & not Skinned) are included, then what should I do?
Do I have to skin it to a bone? Is that the only way? I hope there’s another way…
I’m still learning unreal so… please help, thanks.