Dark patches in Capture's preview pane (top-down map of the scanned area) can develop for a number of reasons.
However, they all mean the camera could not pick up any depth information from that point.
Area is Obstructed or Not in View
The Matterport camera cannot see behind obstacles, so these areas are left black.
For example, in the middle red box in the image above, the camera (indicated by the blue dot) cannot see past the couch.
In addition, the camera cannot see directly above or below itself. This explains the dark ring around the camera (top red box in above image).
Area is Out of Range
The Matterport Pro and Pro2 3D Cameras have a maximum range of about 15 ft (5 m), depending on the environment.
Anything beyond that range will not accurately reflect the infrared light used by the camera to sense depth, and will just appear as black or dithered as indicated in the bottom right square above. This is especially common in large empty spaces.
Area is Very Bright
The Matterport Pro and Pro2 3D Camera uses infrared light to sense 3D depth data.
Bright light (especially sunlight) can show up as black when scanning because it contains a lot of infrared light that washes out what the camera can see.
Avoid sunlight by closing drapes/blinds, or by scanning at less sunny times. Learn more.