Why did iMessage stop working with IOS 10.0.2 update?

HI all -

yesterday I updated my iPhone 6 Plus from IOS 10 to IOS 10.0.2. Now - iMessage will not work. I can send texts, but only in SMS. I rebooted, turned iMessage on and off, signed in and out - tried everything I could find on here about iMessage and IOS 10. I even restored to original settings thinking a setting got changed. Still nothing. Any help or suggestions out there please? Thanks in advance