As Richard has indicated, cut planes are likely to be your issue assuming the wall is at the right elevation for what you want to show. As a crude guide...
A wall completely below the cut plane will show in outline only
A wall intersecting the cut plane will have fills
A wall above but falling within the cut plane range will be shown as overhead
I have found cut planes to be quite entertaining as you chase around adjusting their range settings and altering element display settings to make sure they show what you want.
Apple iMac Intel i9 / macOS Sonoma / AC27UKI (most recent builds.. if they work)