When using the iOS Studio Viewer App you are unable to view any models including the ones that are installed by default inside the application.
When you try to open models in the Visualizer App on the iPhone or iPad you get a spinning wheel and the model never opens.
No matter which model you open, the below screen will show while the spinning wheel will keep spinning.
(in the latest iOS Studio Viewer app, you'll get a proper warning message stating that access to the Camera was denied, and that this needs to be granted in order for you to view files).
There is a problem with the Studio Viewer if the Camera is not enabled.
Studio Viewer iOS