why wont my character jump ,why can my character move left and right but cant jump

Questions & Answers
1

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class PlayerController : MonoBehaviour
{

//Movement
public float speed;
public float jump;
float moveVelocity;

//Grounded Vars
bool isGrounded = true;

void Update()
{
    //Jumping
    if (Input.GetKeyDown(KeyCode.Space) || Input.GetKeyDown(KeyCode.UpArrow))
    {
        if (isGrounded)
        {
            GetComponent<Rigidbody2D>().velocity = new Vector2(GetComponent<Rigidbody2D>().velocity.x, jump);
            isGrounded = true;
        }
    }

    moveVelocity = 0;

    //Left Right Movement
    if (Input.GetKey(KeyCode.LeftArrow) || Input.GetKey(KeyCode.A))
    {
        moveVelocity = -3;
    }
    if (Input.GetKey(KeyCode.RightArrow) || Input.GetKey(KeyCode.D))
    {
        moveVelocity = 3;
    }

    GetComponent<Rigidbody2D>().velocity = new Vector2(moveVelocity, GetComponent<Rigidbody2D>().velocity.y);

}
//Check if Grounded
void OnTriggerEnter2D(Collider2D col)
{
    isGrounded = true;
}

}

2

your issue is here :

 //Jumping
         if (Input.GetKeyDown(KeyCode.Space) || Input.GetKeyDown(KeyCode.UpArrow))
         {
             if (isGrounded)
             {
                 GetComponent<Rigidbody2D>().velocity = new Vector2(GetComponent<Rigidbody2D>().velocity.x, jump);
                 isGrounded = false;  //change this line to false instead of ture
             }
         }