AddForce not working on Instantiated prefab

I've been trying to get projectile/prefab bullets in a top down 2d project here's the code:

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class Shooterer : MonoBehaviour {
     public GameObject bullet;
     public float bulletspeed;
     private GameObject instbullet;
     private Rigidbody2D rb;
     private bool Canfire;
     
     void Start () {
         Canfire = true;
     }

     void Update () {
         if(Canfire){
             //getting direction of firing 
             if (Input.GetKey (KeyCode.UpArrow)){
                 fire ();
                 rb.AddForce (instbullet.transform.up * (bulletspeed/150.0f));
             }
             if(Input.GetKey (KeyCode.DownArrow)){
                 fire ();
                 rb.AddForce (instbullet.transform.up * (-bulletspeed/150.0f));
             }
             if(Input.GetKey (KeyCode.LeftArrow)){
                 fire ();
                 rb.AddForce (instbullet.transform.right * (-bulletspeed/150.0f));
             }
             if(Input.GetKey (KeyCode.RightArrow)){
                 fire ();
                 rb.AddForce (instbullet.transform.right * (bulletspeed/150.0f));
             }
         }
     }

     void fire(){
         if (Canfire) {
             //instantiate bullet
             instbullet = Instantiate /*(bullet, new Vector3(0,0,0), Quaternion.identity);*/ (bullet, new Vector3 (gameObject.transform.position.x, gameObject.transform.position.y, gameObject.transform.position.z), Quaternion.identity);
             //get bullet rigidbody
             rb = instbullet.GetComponent<Rigidbody2D> ();
             Canfire = false;
             Invoke ("Canfiretruetime", 0.25f);
         }
     }
     //Allow player to fire again
     void Canfiretruetime(){
         Canfire = true;
     }
 }