OnTriggerEnter2D not working

in my game the bullet is instantiated and is supposed to travel across the screen and be deleted if it hits the boundary. i setup an empty game object with a box collider2D and gave it the script bellow. i also attached the settings for my bullet prefab. what am i doing wrong?

public class BoundaryTrigger : MonoBehaviour {

void onTriggerEnter2D (Collider2D other) {
    if (other.gameObject.tag == "Projectile") {
        Debug.Log("detected");
    }
    
}

}

Case sensitivity matters. The method is called OnTriggerEnter2D(), not onTriggerEnter2D().