Did you guys forget that you need to have a rigid body attached to one of the game objects that are colliding to activate the trigger?
Check if this isn’t the problem!
I forget the link to the collision matrix, but try to find something about triggers collision on documentation and you will know about what I’m talking about.
Note: Will be better apply the rigid body to the game object that is moving, not the static one. Please check the documentation for further information.