It could be the 'Floor Plan Display' in the object settings - I find "Symbolic' works best for most circumstances.
I also set the walls to be the same.
Or it could be your Renovation Filters.
Check if your windows are 'New', 'Existing' or 'To Be Demolished' and also check the reno filter settings to see what happens to these type of elements (i.e. they may be set to 'Hide').
Barry.
One of the forum moderators.
Versions 6.5 to 27
Dell XPS- i7-6700 @ 3.4Ghz, 16GB ram, GeForce GTX 960 (2GB), Windows 10
Lenovo Thinkpad - i7-1270P 2.20 GHz, 32GB RAM, Nvidia T550, Windows 11