how to prevent multiple jumps using isGrounded properly?

I'm developing a First-Person game using the new input system. The issue I'm facing is jumping. when I press Space to jump, I can jump again while the player is still in the air, I can jump multiple times till the player fly. This should not happen. the player should jump only when he is grounded.

public class MyPlayerMovement : MonoBehaviour
{

    private InputMaster controls;
    private float moveSpeed = 8f;
    private float runSpeed = 50f;
    private Vector3 velocity;
    private float gravity = -9.8f;
    private Vector2 move;
    private float run;
    private float jumpHeight = 2.4f;
    private CharacterController controller;
    public Transform ground;
    public float distanceToGround = 0.4f;
    [SerializeField] LayerMask groundMask;
    private bool isGrounded;
    private bool isRunning; 

    private void Awake()
    {
        controls = new InputMaster();
        controller = GetComponent<CharacterController>();
        controls.Player.Run.started += _ => isRunning = true;
        controls.Player.Run.canceled += _ => isRunning = false;
    }
     void Update()
    {
        Grav();
        PlayerMovement();
        Jump(); 
        // check if Run button is pressed
        if (isRunning)
        {
            run = controls.Player.Run.ReadValue<float>();
            Vector3 running = (move.y * transform.forward) + (move.x * transform.right);
            controller.Move(running * runSpeed * Time.deltaTime);
        }
    }

    private void PlayerMovement() 
    {
        move = controls.Player.Movement.ReadValue<Vector2>();
        Vector3 movement = (move.y * transform.forward) + (move.x * transform.right);
        controller.Move(movement * moveSpeed * Time.deltaTime);
    }

    private void Jump() 
    {
        if (controls.Player.Jump.triggered)
        {
            velocity.y = Mathf.Sqrt(jumpHeight * -2f * gravity); 
        }
    }

    public void OnRun()
    {
        isRunning = !isRunning;
    }

    private void Grav() 
    {
        //handeling gravity
        isGrounded = Physics.CheckSphere(transform.position, distanceToGround, groundMask);
        if (isGrounded && velocity.y < 0)
        { 
            velocity.y = -2f;
        }
        velocity.y += gravity * Time.deltaTime;
        controller.Move(velocity * Time.deltaTime);
    }

    private void OnEnable()
    {
        controls.Enable(); 
    }

    private void OnDisable()
    {
        controls.Disable(); 
    }
}

I tried to fix this issue by changing the jump condition to this :

if (controls.Player.Jump.triggered && isGrounded)

but now the player does not jump at all. How can I make this work?