When a page asks for the camera on a Meta Quest, Meta Browser's dialog comes with Virtual cameras ticked and Headset cameras not. Accepted as it stands, the page gets a virtual camera and every frame is black. Tick Headset cameras, then Allow. At 0xr.space a short moving picture beside the dialog rings the box to tick, and the dock says Tick Headset cameras, then Allow.
If Allow was pressed with only Virtual cameras, the browser does not ask again. Open the Quest's Settings, then Privacy & safety, then Browser, turn on Headset cameras and press Scan again. The free Model Explorer app runs on the same browser, so it needs the same switch; it opens that page for you and has its own camera switch too.
The browser was given a virtual camera rather than the cameras that see the room. Only Headset cameras shows the room.
The app has its own camera switch as well as the browser's. Turn the camera on on the page it opens, then press Scan again.
See the privacy page at https://0xr.space/privacy/ for what the camera features send and keep.