Mesh collider from 3d model not triggering collision with plane

I have a plane that represents a ‘tar pit’ ( y = 0.2 ) that I place on the terrain ( y = 0 ) that I have enemies ( y = 0 ) run over and I want to trigger an event.

I can successfully get other objects ( a cylinder representing a gun tower ) to interact with my enemies, but I can’t for the life of me get anything to happen when they cross the plane.

If I move the plane at game time into the enemies, I get the debug statements from both of the OnTriggerEvents ( the enemy and the plane ) , but when the plane is npt moving I can’t get any of the functions executing.

Both the enemy and the plane have box colliders with ‘Is Trigger’ checked, am I missing something ?

Thanks!

If the enemies are CharacterControllers, you may place a trigger volume in the tar pit - when an enemy enters the trigger, OnTriggerEnter events will be sent to both, the enemy and the tar pit.

If the enemies aren’t CharacterControllers, they must have a rigidbody to be detected by the trigger, and their colliders must not be set as triggers (even because they would fall like rocks through the terrain in this case).