There are two reasons why you can't see the inside of the room in 3D view:
Reason 1: Automatic display/hiding
When Automatic display/hiding is disabled, all walls and ceilings will be shown and the view of the room will be from the outside. If disabled, the icon located under the View tab on the second row of icons, will be grey:
Click on the Automatic display/hiding icon to enable. The icon will now be green:
Now the walls and ceiling will automatically hide as the camera is panned around the room.
Reason 2: The floor is missing
The floor can be deleted in Innoplus. If this happens all of the walls will be shown automatically even if Automatic display/hiding is enabled.
To fix this, right-click on a wall and select Renew floor.
Note: The view picker indicates that the floor is missing by displaying a white background. The left image is correct, the right image shows there is no floor.
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