Did you ever find a solution to this problem? I think I have the same problem. My supply line doesn't work. Sanctuary doesn't even show on my Pip-Boy in the Data/Workshops tab. Did you move your workbench? I ask cause I did and and only that one. I looked for a console command to reset its position, but all i could find was to reset the whole settlement back to it's original state, and I've put a lot of time and mats into Sanctuary.