I can't enable simulate physic on instanced static mesh

doesn’t work on any static mesh even though i can simulate physic when I put one static mesh in my scene

That field is disabled for primitive components without collision and/or physics bodies, so I’m assuming your static mesh doesn’t have any collision set up. Open that rock mesh asset and add collision (for example, through this dropdown):

Here’s a more detailed tutorial (which mentions why this exact field is being grayed out):

Hi, thanks for your fast reply. As I said, I can simulate physics when I put my static mesh on my scene wich means it has collisions, I already checked that and it has collisions, the problem is when I try to put it in an instanced static mesh in an actor blueprint.

here are the collisions showed :