I’ve been trying to follow the examples posted here dating from 2015 to 2019 on running a bus from the main sheet to a subordinate sheet and have come upon a roadblock. When I asked about it in kicad@libera.net, I was told this may be a bug, not me now knowing what I’m doing. Here, I’ve broken the problem down to the simplest possible example.
The problem is the label in the root-sheet.
Inside of the subsheet-rectangle you have to place a hierarchical sheet pin (not a simple label / bus label).
So delete the D[0…7] inside the rectangle. Than use the “import a hierarchical sheet pin”-button on the right side toolbar and now with this activated tool click inside the subsheet-rectangle.