Pun 2 - The type or namespace name 'NetworkVariable<>' could not be found

I am trying to create NetworkVariables in a PUN 2 project, but I keep getting this error: Assets\scripts\GameManager.cs(12,19): error CS0246: The type or namespace name 'NetworkVariable<>' could not be found (are you missing a using directive or an assembly reference?)


while this error does say line 12, I am gettting it for lines 12, 16, and 20.


here is the part of "GameManager.cs" that the issue is found in:

using System.Collections;

using System.Collections.Generic;

using UnityEngine;

using UnityEngine.SceneManagement;

using UnityEngine.UI;

using Photon.Pun;

using Photon.Realtime;


public class GameManager : MonoBehaviourPunCallbacks

{

  public static bool DefaultSettingsActive = false;

  public static NetworkVariable<float> startCards = new NetworkVariable<int>();

  public GameObject startCardsSlider;

  public Text startCardsSettingDisplayText;


  public static NetworkVariable<float> deckSize = new NetworkVariable<int>();

  public GameObject deckSizeSlider;

  public Text deckSizeSettingDisplayText;


  public static NetworkVariable<bool> p1GoesFirst = new NetworkVariable<int>();

  public GameObject p2GoesFirstButton;

  public GameObject p1GoesFirstButton;


  public static bool devModeIsActive = false;

  public InputField devMoveActivateInputField;

  public GameObject activateDevModeButton;

  public GameObject deactivateDevModeButton;

  public bool cheatConsoleIsOn = false;

  public GameObject CheatConsoleParent;

  public GameObject cheatConsoleActivate;

  public GameObject cheatConsoleDeactivate;

  public bool unlimitedActions = false;

  public GameObject unlimitedActionsParent;

  public GameObject unlimitedActionsActivate;

  public GameObject unlimitedActionsDeactivate;


  public GameObject roomSettingsUI;

  public bool roomUIUp = false;


  void Awake ()

  {

    if (DefaultSettingsActive != true)

    {

      startCards.Value = 6f;

      deckSize.Value = 60f;

      p1GoesFirst = true;


      DefaultSettingsActive = true;

    }

  }


How can I fix the error?