Grid Forecast says "No Location Available" - SOLVED

So I had this problem, where I would open the Home app on my iPhone and there's a "Grid Forecast" feature that would say "No Location Available". I wanted to see the forecast, and I live in California so the feature is supported here.

In Location Services, the Home app already had permission to use my precise location, so that wasn't the issue. And my Contacts card for "me" has my correct address. These two things were suggested as potential sources of trouble in other forums, but neither solved the problem for me.

Well, I found a solution. Looking at Settings->Privacy & Security->Location Services->System Services->HomeKit, location services was disabled for HomeKit. Turned this on and Grid Forecast now works!

This was probably turned off by me a long time ago when I turned off location services for everything I wasn't using, just to increase privacy, and then of course I forgot all about it. It sure would be helpful if Apple could provide feedback within the app to indicate what setting was causing the problem, but I imagine this is a rare problem because I bet very few people ever turn any of these settings off.

Hope this helps someone else in the future.