Question Object with sprite renderer not appearing in AR, but shows up in-editor

Hi Unity experts. I'm running into an issue with AR where a prefabbed game object's sprites doesn't appear when instances into 3D space when in AR, but is perfectly visible when instance in Editor. This was working properly before in 2019, but seemed to have stopped working after migrating to Unity 2020. But I'm not sure if that's the cause or the Quality setting under which the app is built.

I have a prefab with a "shadow" gameobject under it's hierarchy:

View attachment 1052498

It's just a simple game object with a sprite-renderer:
View attachment 1052501

The prefabs are packed into a Unity Asset Bundle and loaded in at run-time by the application. I have a debug mode that pretty much runs the app in-editor for testing purposes, and loading the prefab shows the shadow just fine, so it's not a missing texture or disabled model that's the cause.

View attachment 1052504

This object is missing or invisible in AR when on the phone. I checked "under" the prefab to make sure the sprite isn't unidirectional that is pointed downwards, making it invisible from the top. I'm wondering why that is. Any help would be appreciated.

Maybe something do with the quality settings when built? Mobile devices uses the Medium settings in Unity. Not sure if that setting has changed between 2019 and 2020 to make sprites not visible.

-Thanks.