Please see this model:
I want to move the selected edge up, forming a roof on the right hand side of this box. Eventually I want the roof to meet and be at the same pitch as the higher roof, but I’m just playing about with the shape at the moment.
However, I can’t drag the edge up. If I have the box separate to the main house, it works fine. What have I done which stops the roof being dragged up? Did I make a mistake having separate shapes connected to each other?