Haha, Thanks, everybody. iOS 10 was my problem. And updating to iOS 10.1 did work.
iOS 10.1 fixes:
Other improvements and fixes
Improves Bluetooth connectivity with 3rd party accessories
Improves AirPlay Mirroring performance when waking a device from sleep
Fixes an issue where playback would not work for iTunes purchased content when the “Show iTunes Purchases” setting is turned off
Fixes an issue where certain selfie apps and face filters used with the FaceTime HD Camera on iPhone 7 and iPhone 7 Plus did not display a live preview
Fixes an issue in Health where individual strokes are converted to separate characters when using the Chinese handwriting keyboard
Improves performance of sharing websites from Safari to Messages
Fixes an issue in Safari that caused web previews in tab view to not display correctly
Fixes an issue that caused certain Mail messages to be reformatted with very small text
Fixes an issue that caused some HTML email to be formatted incorrectly
Fixes an issue that in some cases caused the search field to disappear in Mail
Fixes an issue that could prevent Today View Widgets from updating when launched
Fixes an issue where Weather widget sometimes failed to load data
Fixes an issue on iPhone 7 where Home Button click settings would not appear in search results
Fixes an issue that prevented spam alert extensions from blocking calls
Resolves an issue that could prevent alarm sounds from going off
Fixes an issue where audio playback via Bluetooth would cause the Taptic engine to stop providing feedback for some users
Resolves an issue preventing some users from restoring from iCloud Backup
Source:
https://support.apple.com/kb/DL1893
Otherwise, for other users, if upgrading does not work, then you should check the list in this article
https://iphonebyte.com/fix-iphone-al...k-not-working/ I saw that all the possible causes listed here, but none of them work for me