I set reminders a lot, as I am very forgetful. In iOS 9, every single one I set would always popup, and display a lock screen notification until I cleared it or marked as completed. In iOS 10, I've noticed that about 1/3 or 1/2 of them never display any sort of notification. They don't popup nor do they appear on the lock screen. The only reason I know I missed a reminder is if there is a badge icon number on the app icon. i did a restore from a previous iPhone 6+ to this one, wondering if a factory reset would fix it.