Widgets not refreshing (solved!) News widget not updating, Reminders widget not refreshing
My problem: Widgets were not refreshing. Reminders widget wouldn't update/refresh - it was showing reminders that I had already deleted and NOT showing reminders that have just popped up. News widget was showing news stories from last night that were definitely not still current (articles, headlines, etc. had changed in the app but the widget was still showing the old version).
Solution that worked: Changed language. Settings > General > Language & Region > iPhone Language (changed from US English to Canadian English). Takes a moment to implement the change but as soon as I could get out of settings, the widgets had all updated. I changed it back to US English. I "tested" it several times by making changes to reminders and every time, it instantly updated the widget. So, it appears that this solution actually fixed the problem rather than simply causing one refresh.
Before I posted here, I found the solution, but I came here to share the solution to get some good karma, since I've had helpful people here solve lots of problems for me in the past. Credit for the solution: http://appletoolbox.com/2016/07/ios-10-widgets-not-working-how-to/
iPhone 6s, iOS 10, 10.0.1