While in a Perspective render, you are unable to see one or more of your walls or sloped ceiling.
The walls and or sloped ceilings not being visible is due to having the hide walls feature switched on. To turn it off:
1. While in a Perspective render, click the VIEW tab in the Ribbon.
2. Click the Hide Walls button, located in the Display section.
3. Verify that the walls and/or sloped ceiling are now visible.
Although this feature can be very useful when trying to achieve the correct viewing angles for your perspective, you may also need to switch it off in certain cases.