Need help with enemy script (C#)(2D)

So I a script where the ufo is supposed to go the other direction when it touches a certain object, but the bool I am using to do this wont go true on the collision, here is my script for it.

 float speed = 3f;

 public bool returnRight;
 
 void Start () {

 }

 void FixedUpdate (){
     if (returnRight == true){
         MoveLeft ();
     }
     if (returnRight == false) {
         MoveRight ();
     }
 }
 void OnCollisionEnter2D (Collision2D other){
     if (other.transform.tag == "ReturnRight1") {
         returnRight = true;
     }
     if (other.transform.tag == "ReturnLeft1") {
         returnRight = false;
     }
 }
 void MoveRight (){
     transform.Translate(Vector3.right * speed * Time.deltaTime);
 }
 void MoveLeft (){
     transform.Translate(Vector3.left * speed * Time.deltaTime);
 }