iMessage stopped syncing I have an iPhone (iOS 10) and a macbook (macOS 10).
My SMS/iMessages used to be in sync between my computer and my iPhone.

At some point, not sure when, they stopped syncing.


Both devices are connected to my Apple ID.
Handoff is enabled.
iMessage is enabled.
First of all, I've had a less than prefect experience with messages being delivered to both Mac and iPhone which I largely attribute to non-Apple devices. 

To your problem, have you tried un-ticking phone numbers/email accounts and signing out on both devices? Quit app then re-lauching and signing back in?