Why doesn't my jump reset?

Questions & Answers
1

public Vector2 jump;
public float jumpForce = 2.0f;

float horizontal;
float vertical;
Rigidbody2D rb;
IEnumerator dashCoroutine;
public bool isGrounded;

bool isDashing;
bool canDash = true;
float direction = 1;
float normalGravity;

void Start()
{
    rb = GetComponent<Rigidbody2D>();
    normalGravity = rb.gravityScale;
    jump = new Vector2(0.0f, 4.0f);
}

void Update()
{
    if (horizontal != 0)
    {
        direction = horizontal;
    }
    horizontal = Input.GetAxisRaw("Horizontal");
    vertical = Input.GetAxis("Jump");
    if (Input.GetKeyDown(KeyCode.LeftShift))
    {
        if (dashCoroutine != null)
        {
            StopCoroutine(dashCoroutine);
        }
        dashCoroutine = Dash(.1f, 1);
        StartCoroutine(dashCoroutine);
    }
}

void OnCollisionStay()
{
    isGrounded = true;
}

private void FixedUpdate()
{
    rb.AddForce(new Vector2(horizontal * 20, 0));

    if (Input.GetKeyDown(KeyCode.Space) && isGrounded)
    {
        rb.AddForce(jump * jumpForce, ForceMode2D.Impulse);
        isGrounded = false;
    }
    if (isDashing)
    {
        rb.AddForce(new Vector2(direction * 10, 0), ForceMode2D.Impulse);
    }
}

IEnumerator Dash(float dashDuration, float dashCooldown)
{
    isDashing = true;
    canDash = false;
    rb.gravityScale = 0;
    rb.velocity = Vector2.zero;
    yield return new WaitForSeconds(dashDuration);
    isDashing = false;
    rb.gravityScale = normalGravity;
    rb.velocity = Vector2.zero;
    yield return new WaitForSeconds(dashCooldown);
    canDash = true;
}
2

Chances are judging by the fact your are using a RigidBody2D you have 2D colliders. In that case you want to use OnCollisionStay2D as opposed to OnCollisionStay.