Unity 2D Jump script

So I was trying to implement double jumping in my game, which doesn't work. And now, somehow, not only can't my players double jump, they can't even jump either!

update: they can jump now, still can't double jump though.

This is my whole movement script:

using UnityEngine;

namespace Players
{
    public class Actor : MonoBehaviour
    {
        //in order to control both players using 1 script.
        public int playerIdx;

        //Variables.
        public float movementSpeed = 150f;
        public float jumpForce = 250f;

        //Ground stuff.
        public LayerMask whatIsGround;
        public bool grounded;

        //boolean stuff.
        private bool facingRight;
        private bool moving;

        //Needed to check if player is on the ground.
        public Transform groundCheck;

        //Limit player's movement speed.
        public float maxMovementSpeed = 400f;

        //Double jump stuff.
        private bool doubleJumpReady;

        //rb
        private Rigidbody2D rb;


        // Start is called before the first frame update
        void Start()
        {
            doubleJumpReady = true;
            rb = GetComponent<Rigidbody2D>();
            facingRight = true;
        }

        // Update is called once per frame
        void FixedUpdate()
        {
            SlowDown();
        }

        private void LateUpdate()
        {
            grounded = Physics2D.OverlapCircle(groundCheck.position, 0.1f, whatIsGround);

            if (grounded)
                doubleJumpReady = true;           

        }

        private void SlowDown()
        {

            if (moving) return;

            //if player is not moving, slow them down.
            if (rb.velocity.x > 0.2f)
                rb.AddForce(movementSpeed * Time.deltaTime * -Vector2.right);
            if (rb.velocity.x < -0.2f)
                rb.AddForce(movementSpeed * Time.deltaTime * Vector2.right);
        }

        public void Move(int dir)
        {
            //Flip the player.
            Flip(dir);

            //Moving the player.
            moving = true;

            float xVel = rb.velocity.x;            //Get x velocity.

            if ( dir > 0)
                rb.AddForce(movementSpeed * Time.deltaTime * Vector2.right * dir);
            else if (dir < 0)
                rb.AddForce(movementSpeed * Time.deltaTime * Vector2.right * dir);
            else if (dir == 0) { }  //do nothing.

            //Help player turn around faster.
            if (xVel > 0.2f && dir < 0)
                rb.AddForce(movementSpeed * 3.2f * Time.deltaTime * -Vector2.right);
            if (xVel < 0.2f && dir > 0)
                rb.AddForce(movementSpeed * 3.2f * Time.deltaTime * Vector2.right);
        }

        private void Flip(int dir)
        {
            if (facingRight && dir == -1 || !facingRight && dir == 1)
            {
                facingRight = !facingRight;
                transform.Rotate(0f, 180f, 0f);
            }
        }

        protected void Jump()
        {
            if (grounded)
            {
                rb.AddForce(Vector2.up * jumpForce);
                grounded = false;
                doubleJumpReady = true;
            }
            else if (!grounded && doubleJumpReady)
            {
                rb.AddForce(Vector2.up * jumpForce);
                doubleJumpReady = false;
            }
        }       
    }
}

I don't know if it is because of my jump script, or my player script:

void Update()
{
    if (playerIdx == 1)
    {
        if (Input.GetKey(KeyCode.A))
            Move(-1);
        if (Input.GetKey(KeyCode.D))
            Move(1);
        if (Input.GetKey(KeyCode.W))
            Jump();
    }

    if (playerIdx == 2)
    {
        if (Input.GetKey(KeyCode.LeftArrow))
            Move(-1);
        if (Input.GetKey(KeyCode.RightArrow))
            Move(1);
        if (Input.GetKey(KeyCode.UpArrow))
            Jump();
    }
}

So how can I fix this?