Thank you Master. I did that suggested in the “Test.dae” object that I uploaded to SecondLife and Rezzee it on the ground and made the change to “Prim” and now you can see the physics.

Thank you for the object. I uploaded Test.dae with the physics shape set to 'high' LOD, which indeed shows a hole for the physics shape for the preview (see screenshot).

Once uploaded and rezzed in-world, the default physics shape of the object is set to 'convex hull', which causes it to collide like a regular box (not hollow).

However, if the object is set to "Prim" physics via Build -> Features -> Physics Shape Type, it takes on the collision shape of a door frame, and avatars etc. can move through the center of it, like so: https://youtu.be/IAkNEcvMlnM

Is the 'Prim' physics shape option available for you? If so, I believe that's the option you want for this object.

Note that if the object has "Physics" enabled to make it dynamic, it will fall back to 'convex hull' shape. If you need the object to have a hollow shape when in convex hull mode, you will need to use 'convex decomposition', which is described in https://wiki.secondlife.com/wiki/Mesh/Mesh_physics