projectiles not coliding with character

Hi There. I'm having the following problem:

I'm doing a 2D infinite runner, and i plan that at some point a kind of projectile will be shot at the character from the other side of the screen, but when they are shot they don't connect, either with the character or with the triggers to destroy them in case the character evades them.

Here's my Code

 PlatformerCharacter2D life;
 HUDScript hud;
 void OnTriggerEnter2D (Collider2D other)   // when the kunai hits something it can
         {
     if (other.tag == "Ground")   // if collides on ground, be destroyed
         {
         Destroy (this.gameObject);
 
         }
     else if (other.tag == "Destroyer") // if collides with back destroyer, award score (meaning the player dodged it
         {
         hud = GameObject.Find ("Main Camera").GetComponent<HUDScript>();
         hud.IncreaseScore (10);
         }
         if (other.tag == "Player")                // if it hits the Player, call it's Vitality Class, to reduce his life by 1
         {
         life = other.GetComponent<PlatformerCharacter2D>();
         life.Vitality(-1);
         Destroy (this.gameObject);
         }

The Character, projectile and destroyer objects are all on the same layer, with Z position at 0, and with correct the tags, but they don't interact, but the player, the ground and the destroyers do...

Anyone see what may be wrong? Thanks in advance...