OnTriggerEnter doesn't work

I'm currently using this for when the object collides with another object:

 void OnTriggerEnter(Collider2D other)
     {
         if(other.tag == "Player")
         {
             hitPlayer = true;
         }
     }

Unless that way I scripted that is wrong then I really have no idea what is going on.

Basically no matter what I do, that function won't go off despite colliding with the player. The object holding that script has been set to a trigger with both objects having a rigidbody. Their collides are both big enough to collide with each other but that OnTriggerEnter function just won't run and I really don't know why.

Is there something else I've forgotten about when using OnTriggerEnter as it's worked all the other times I've used it.