When the height of your walls is different on the same level, go to the wall settings, and unclick on the icon "stick to slab", so you can enter a new height.
If you have upstairs windows that are not visible, you need to remove the check mark to the ceiling, as the site detects that the wall below that you have set higher goes up to the top level.
SOME WALLS APPEAR IN 3D WHEN THEY ARE NOT DRAWN IN 2D?
This is probably due to the wall setting as explained above where you have to unclick on the icon "stick to slab" on the lower floor.
On the lower floor, we notice walls that are higher than the others, the same ones that appear on the upper floor:
In this case, go to the wall parameters and unclick "stick to slab":
Returning to the floor where the walls appeared in 3D when they were not drawn: