These walls have been nothing but exterior - now look - the siding has gone.
i tried to paint - but siding was not an option.
how do convert them back to exterior walls with siding???
typical reason a wall does not act as an exterior wall is because the "room" is not closed all around to actually form a room....also a reason why a floor may not exist...
so go around those walls and be sure each wall correctly connects to the next wall and the room is fully enclosed with connected walls
if still a problem, suggest you post the .bld file for others to look at