If you insist on separate walls for each storey, then you will need to add an empty opening to the second wall.
A door or window can only belong to one wall.
Otherwise use a single wall that spans both storeys.
Barry.
One of the forum moderators. Versions 6.5 to 27 i7-10700 @ 2.9Ghz, 32GB ram, GeForce RTX 2060 (6GB), Windows 10 Lenovo Thinkpad - i7-1270P 2.20 GHz, 32GB RAM, Nvidia T550, Windows 11