I personally don't recall ever doing a restore power quest at that POI. Regardless of quest type, that POI always involves pushing 3 buttons (with power restore quests, you're interacting directly with the generators, not buttons) so it sounds like you're doing something other than power restore, but I could very well be wrong. Whatever the case, once you activate all 3 buttons, the garage door for the last house (the one that looks finished) will open revealing the loot room and usually several zombies and a very friendly zombie bear. Depending on the quest type, just clear out the last house.
I've quested at this POI several times and the only issue I've had was my first time going through and not knowing where to start. It's very non-linear. I've never had it bug out on me. So if you're sure you've cleared out the entire POI, it sounds like your game is bugged. If that's the case, verify your steam game files. Hopefully this helps.
