Left mouse button not working

I am trying to simply play an animation in my PlayerCombat.cs script, (following steps from a Brackeys vid)

// Update is called once per frame
void Update()
{
if (Input.GetKeyDown(“Fire1”))
{
Attack();
}
}

    void Attack ()
    {
        //Play an attack anim
        animator.SetTrigger("Attack");

        //detect enemies in range of the attack
        //apply damage
    }

I have done all things for the animator to work in unity, but its just not working. how do I fix this, does it have to do with the input system?

The correct one is Input.GetButtonDown (“Fire 1”)

 void Update () 
 {
 if (Input.GetButtonDown ("Fire1")) 
 {
    Attack (); 
 }
 }

 void Attack ()
 {
     //Play an attack anim
     animator.SetTrigger("Attack");
     //detect enemies in range of the attack
     //apply damage
 }