Actually, that helped. There are basically four things that can cause this problem that I am aware of: materials, meshes, puzzles and the blend file.
So we ruled out materials… I then downloaded you project file and stripped out all meshes and materials, cleaned/purged the file and then inserted a default cube and tested that.
That resulted in the same problem…. so we were down to puzzles and the blend file.
I then created a default project and then exported your blend to the gltf for this project without puzzles and it did not work again.
So having ruled out materials, meshes and puzzles…the only remaining item was the blend file.
Starting with a new Blend file…I deleted the default cube and lights and appended all your objects.
Tried that and it now is viewable on iPhone.
https://cdn.soft8soft.com/AROAJSY2GOEHMOFUVPIOE:184ff32db5/applications/Gridscape-AR/Gridscape-AR.html
I don’t know the cause of why your blend file is not working properly but simply appending solved the problem so I will let you chase it down from there if you choose.
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