I got a problem with new hair system

I follow the doc Hair Rendering and Simulation Quick Start | Unreal Engine Documentation to learn the new hair system.Everything is fine except the Bind Groom to Skeletal Mesh.

When i enable the this option ,My hair always disappeared like this.

The mesh created by daz3d G8F.And hair attach to head bone.

I think maybe something wrong with the girl chracter. I try to use the UE4 Mannequin mesh.The same problem.

If i don’t check the “Bind Groom to Skeletal Mesh”,everything is fine.

So,how do i fixed that problem ?Any help will be appreciate.

maybe you need simple head