Wall not appearing in 3D

[Paopao]

Hi,
can anyone explain me why this wall doesn't appear on the 3D? It does appear in plans. I have added the element on the last floor and have cut part of the roof to adjust it. Is that the reason?

Thanks
PP

[Paopao]

I have solved. the walls connected to the roof were "cut" once I modified the roof pitch geometry: they were connected.