Use the Physics Based Gravity tool on a imported object

Hello,

I'm using Twinmotion 2023 on PC. I've imported an object with a lot of pieces inside. I want to use the Physics Based Gravity tool on the full object but I can't ! All pieces of object are falling separately. Do you have a tip to make a full hierachised object fall with the tool ? (sorry for my english).

Is it possible to make a video with the gravity tool ?

Thank you by advance