I am new to VR programming in unity and for my first project I followed the google quick guide to use the cardboard, I was able to implement everything, it fixes several errors and I was able to compile my app and run it on my device correctly. But the main problem is that I can't move the camera with the gyroscope of my cell phone, much less with my fingers, and also you can't see the double view that they have for cardboards, as I saw that they have many tutorials that follow this guide. I don't think it's a problem with my device because in the game window in Unity when I run it I can't move either (In the tutorials I saw that they do it with Alt + Click).
This is the link of the Guide: https://developers.google.com/cardboard/develop/unity/quickstart?hl=es-419
This warning appears in my MainCamera
The referenced script (Unknown) on this Behaviour is missing!
i think i found the mistake
Initializing XR Failed.
UnityEngine.Debug:LogError (object)
VrModeController/<StartXR>d__10:MoveNext () (at Assets/Samples/Google Cardboard XR Plugin for Unity/1.21.0/Hello Cardboard/Scripts/VrModeController.cs:148)
UnityEngine.SetupCoroutine:InvokeMoveNext (System.Collections.IEnumerator,intptr)
I was able to recreate your issue by unchecking the "Cardboard XR plugin" from the XR plugin provider. So make sure you have this checked in "project settings->XR plugin provider". I recreated this issue in Unity version 2021 lts.
From the error provided, it seems XRLoader singleton is not initializing, look into that. I hope it helps.