I’m working on a placement grid that turns red when something is in the grid way and green when nothing is there. While this work with something is move on to the grid, if the grid is move on to something nothing happens.
The trigger event is raised when the rigidbody creates a movement that makes the object’s collider penetrate the trigger’s collider. I suspect that in your case, the objects have a rigidbody or character controller and the grid doesn’t. Try adding a kinematic rigidbody to your grid, disable gravity and freeze all movements and rotations, it should work.