SOLVED An old thread, but no solution was posted. I'm sharing my solution, for others whose desperate searching leads them here. Solution: Disable all mods. I had already reinstalled Fallout 4, and the Creation Kit. But, I immediately installed a handful of my "essential" mods, like Unofficial Fallout 4 Patch. DON'T. I created a separate "Modding" profile in Vortex, with zero mods enabled. Now, in CK I can finally load Concord, Abernathy Farm, etc.