Do you use your Mac to quickly shoot of SMS replies to messages received on your iPhone? If you did, messaging not working on your Mac can be a real pain, especially since you don’t have the speed capability of using a full size keyboard. Here’s how to fix it.
How to fix messages not working on Mac, in Sierra?
This is more of a resetting than a fix. First, close messages app on your iPhone and also turn it off. Then, put it in Airplane mode and then disable airplane mode after a few seconds. What this temporary airplane mode engagement does is severe all connections to any networks that is essential for this reset.
Now, restart messages on your iPhone and wait for it to be verified with your iPhone number. This will also automatically register (again) with your iMessages.
Also, reset text forwarding in order to receive a new code that you can enter on your iPhone. This simple resetting should bring messaging back to life, on your Mac.