Problems with physics assets

Hi, I’m new to the unreal and I’m not good at English so sorry for mistakes.

I need to add the physics asset in my object, but when I add strange things happen.

In this image, I added an asset in a bone and it worked.
In this image, I added the second asset but it didn’t worked.

I’ve tried with other objects but only had success with unreal objects.
Can someone help me ? thank you.