Why can't I go back to Main Menu at the end my one level? VR

I don’t have a “character”, I just walk through to the end. I have added a cube and game object to lend as the trigger for scene change. But this is what it gives me.

EndLayoutGroup: BeginLayoutGroup must be called first.
UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr, Boolean&)

Why can’t I go back to my main menu?? This seems like it should be something so simple… I wanted to attach OVR Scene Management, but I didn’t see where I should be placing the scene I need to go to…

I’m new to this, sorry.

Absolutely, Thanks @tombedorchestra!

using System.Collections;
using System.Collections.Generic;
using System.ComponentModel.Design;
using UnityEngine;
using UnityEngine.SceneManagement;

public class SceneLoader : MonoBehaviour
public string loadLevel;

private void OnTriggerEnter(Collider other)
    SceneManager.LoadScene(Menu 3D);