App Builds and Installs, but Is opened as a Black Floating Window?

Hi, please see attached. 

Steps to replicate:

- start new unity project. Choose MR template

- Follow instructions to add this camera access functionality from this repo: https://github.com/trev3d/QuestDisplayAccessDemo
- create custom Manifest and mainTemplate.gradle

- Build app, and install with Meta Quest Developer Hub

- Start App, 

- End result is attached photo.

Does anyone know why this is happening?