OnPlayerEnteredRoom/OnPlayerLeftRoom Methods - "No Suitable Method Found to Override"

Hello,

I'm following the tutorial for PUN v2 (https://doc.photonengine.com/en-us/pun/v2/demos-and-tutorials/pun-basics-tutorial/gamemanager-levels)

When I added this section

#region Photon Callbacks


public override void OnPlayerEnteredRoom(Player other)
{
    Debug.LogFormat("OnPlayerEnteredRoom() {0}", other.NickName); // not seen if you're the player connecting


    if (PhotonNetwork.IsMasterClient)
    {
        Debug.LogFormat("OnPlayerEnteredRoom IsMasterClient {0}", PhotonNetwork.IsMasterClient); // called before OnPlayerLeftRoom


        LoadArena();
    }
}


public override void OnPlayerLeftRoom(Player other)
{
    Debug.LogFormat("OnPlayerLeftRoom() {0}", other.NickName); // seen when other disconnects


    if (PhotonNetwork.IsMasterClient)
    {
        Debug.LogFormat("OnPlayerLeftRoom IsMasterClient {0}", PhotonNetwork.IsMasterClient); // called before OnPlayerLeftRoom


        LoadArena();
    }
}


#endregion

I get 2 errors from Visual Studio:

NetworkGameManager.cs(22,30): error CS0115: 'NetworkGameManager.OnPlayerEnteredRoom(Player)': no suitable method found to override

NetworkGameManager.cs(37,30): error CS0115: 'NetworkGameManager.OnPlayerLeftRoom(Player)': no suitable method found to override

I'm inheriting MonoBehaviourPunCallbacks in my class. What's really puzzling me is that other Callbacks, like OnLeftRoom(), are totally working.

I'm using Unity 2018.3.6f1, and VS2017. Pun: 2.7, Photon lib: 4.1.2.9.

Any ideas? I'm stumped.

Thanks!