Attempt to unfreeze constraints using RigidbodyConstraints.None has no effect

Hello I am having trouble unfreezing the constraints of a gameobject in the update method after setting it's constraint(YPosition) in the start method.

By adding a debug.log line in the update method, I can see the log showing up in the console when the spacebar key was being pressed in Play mode. However the ballRb.constraints = RigidbodyConstraints.None didn't seem to be triggered/working.

Edit: I've also tried using this line

ballRb.constraints &= ~RigidbodyConstraints.FreezePositionY;

suggested in another unity answer but to no avail.

Any help or suggestion will be much appreciated.

Code attached below:

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class PlayerController : MonoBehaviour
 {
     public GameObject ball;
     private Rigidbody ballRb;
 
     private Vector3 spawnLocation = new Vector3(0,2.6f,-12);
 
     void Start()
     {
         ballRb = ball.GetComponent<Rigidbody>();
         ballRb.constraints = RigidbodyConstraints.FreezePositionY;
 
         ball.transform.position = spawnLocation;
 
         Instantiate(ball);
     }
 
     void Update()
     {
         if (Input.GetKeyDown(KeyCode.Space))
         {
             Debug.Log("Start");
             ballRb.constraints = RigidbodyConstraints.None;
             Debug.Log("End");
         }
     }
 }