Creating a movie render-to-texture shader works fine on Rift, won't render on Quest

I've created a simple render to texture movie playback system to create a shader for my Unity 2019.3 URP graphics project.
When I apply that shader to my object surfaces and playback on a Rift (or Quest w/Link) the movies all playback correctly.
When I do an Android/Quest build and playback the .apk the movies won't render.
I've tried both URP lit and unlit types and neither work.  Any ideas on why this works for Rift and not Quest?

Note, I'm not by nature a coder or artist so it's highly likely there's a simple fix for this humble audio person :)

thanks!