The asset already has collisions, in fact:
If I create a new blueprint with this skeletal mesh asset containing only this mesh and create the Begin Cursor Over event for it, it works when I play the game. So its not an asset issue.
But, the moment Im using it on my main body skeletal mesh it doesnt work. So it has to be something with it.
If it helps (and I think this is the problem) my shirt is a child target of the main body. Im using Master Pose Component for getting animations on all my meshes :
