This is happening because you've set Is Trigger to true. It seems you need a trigger to detect "respawnPoint", but usually it's not a good thing the "enemyProjectile" to be a trigger. Uncheck Is Trigger in the FireBall object and detect it in OnCollisionEnter (or OnControllerColliiderHit, if the player is a Character Controller):

function OnTriggerEnter( hit : Collider ) { 
  if(hit.gameObject.tag == "respawnPoint") { 
    dead = true;
    HealthControl.LIVES -= 1; 
}

function OnCollisionEnter( hit : Collision ) {
// function OnControllerColliderHit( hit : ControllerColliderHit) {
  if(hit.gameObject.tag == "enemyProjectile") {
    gotHit = true;
    HealthControl.HITS += 1;
    Destroy(hit.gameObject);
  }
}

Yeah, firstly i used: OnControllerColliderHit( hit : ControllerColliderHit)

but problem is If i want the code to work with OnControllerColliderHit (), i need to move with my playerCharacterController. If I stand still, when enemyProjectile hits player, nothing happens.