Bethesda's "next gen" update for Fallout 4 didn't change much about the game itself, but it did manage to cause problems for pretty much every mod out there. The most high-profile casualty was the hotly anticipated Fallout: London, an enormous project that was initially set for release on April 23 (St George's day, of course), but was subsequently delayed while the team set about fixing things.
The good news there is that per the dev team "the end is in sight" (unless you're playing on Epic Games Store)...