This section applies to models created in Autodesk Maya. When exporting your model for AR usage, most file types will only work with Maya renderer materials: Lambert, Phong, PhongE, etc. This area could use deeper research since there are so many materials in Maya, but the ones listed above are known to work with USDZ and GLB/GLTF file types. GLB/GLTF are the file types used for many 3D experiences on Windows and Android.
If you try to export your model with Arnold materials it will most likely not convert correctly in Reality Converter (RC).
The best fix for this is sticking to the three materials mentioned above, and not using any alteration nodes in the Maya Hypershade window.
Another material issue that may arise is texture file loss. The most common encountered error was that FBX models imported into RC did not have the normal map applied to any materials in the model. Simply reassign any missing texture maps in RC and that should solve the issue.
By Juan Diego Torres Brenes LaRoche