NullReferenceException: Object reference not set to an instance of an object
PhotonRoom.OnSceneFinishedLoading (UnityEngine.SceneManagement.Scene scene, UnityEngine.SceneManagement.LoadSceneMode mode) (at Assets/Scripts/photon/PhotonRoom.cs:164)
UnityEngine.SceneManagement.SceneManager.Internal_SceneLoaded (UnityEngine.SceneManagement.Scene scene, UnityEngine.SceneManagement.LoadSceneMode mode)
(at C:/buildslave/unity/build/Runtime/Export/SceneManager/SceneManager.cs:244)
This is the 2D forum. It does not relate to using Photon/Multiplayer. That said, your post is pretty low effort and provides no information apart from indicating you’re getting a NullReferenceException.
I’ll move your post to the scripting forum.
This link there might help: https://forum.unity.com/threads/how-to-fix-a-nullreferenceexception-error.1230297/