Raycast only working once

I have a scene where I have several different shapes. Attached to an object is a script containing the raycast stuff. When the ray intersects an object of a certain shape, I want it do show the shape that it has intersected.

For some reason, It will work the first time but as soon as I move off a shape, the raycast seems to do nothing and it wont recognize that its hit again the second time. It has me stumped cause I have used raycasts before and not run into this problem. It appears that it only runs the update once rather than continuously.

Help greatly appreciated

 using UnityEngine;
 using System.Collections;

 public class RaycastTriangle : MonoBehaviour {
 
 
 // Use this for initialization
 void Start () {
 
 }
 
 void Update() {
 RaycastHit hit;    
     Vector3 up = transform.TransformDirection(Vector3.up);
     if (Physics.Raycast(transform.position, up, out hit))
     {
         if (hit.collider.gameObject.CompareTag("Triangle"))
         {
             print("Triangle");
         }
         
         else if (hit.collider.gameObject.CompareTag("Circle"))
         {
             print("Square");
         }
         
         else if (hit.collider.gameObject.CompareTag("Circle"))
         {
             print("Circle");
         }
         
         else
         {
             print("No Shape");
         }
     }
     Debug.DrawRay(transform.position, up, Color.green);
     
 }

}