ARCore: Skeletal Mesh Can't Display On Phone Screen

Hi All:

I’m learning Google ARCore, but I have a problem.

The left model is from network, the right model is from UE, both using skeletal mesh component.

When I built and installed it in my phone, the left model can’t display but the right one is ok.

This problem has been bothering me for days and I don’t know how to solve it.

These links say it has to do with the bones, but I can’t quite understand, anyone can help me?

Thanks very much and forgive my simple english.