Help with basic photon cloud multiplayer control.

I wrote a basic c# script to move a rigidbody back and forth. When I start the built game I can't control my character. When I start the built game again, so that two copies of the game are running at the same time, I can control both characters, but the control is reversed. Basically player 1 controls player 2 and player 2 controls player 1. Here's my script in case anyone can figure out what I'm doing wrong.

 using System;
 using ExitGames.Client.Photon;
 using UnityEngine;
 using System.Collections;
 
 [RequireComponent(typeof(PhotonView))]
 public class NetworkKeyMovement : Photon.MonoBehaviour {
     void Update() {
         if (this.photonView.isMine&&Input.GetKey("up"))
             rigidbody.velocity = new Vector3(0, 0, 8);
         
         if (this.photonView.isMine&&Input.GetKey("down"))
             rigidbody.velocity = new Vector3(0, 0, -8);
         
     }
 }