Unfortunately, I’ve been having an iMessage issue for the last few months–I can have conversations via Messages on my Mac and conversations via Messages on my iPhone. My iMessages have stopped synchronizing across my devices: no messages I send or receive on my Mac show up on my iPhone, and no messages I send or receive on my iPhone show up on my Mac. It’s like chatting with people from two separate devices, something that Continuity should have solved.
Luckily, there’s a fix. Here’s what I did.
On your iPhone (or iPad)
Launch the Settings app on your iPhone and then tap through to Messages. Once there, swipe down to the section called Send & Receive and open that with a tap.
Once there, you’ll see all the phone numbers and email addresses you’ve registered with your Apple ID. Tap on each one to uncheck or check them. In my case, I needed to check off my email address, since it had somehow become unchecked.
On your Mac
Launch Messages with a click and then open up Preferences, either in the Messages menu or with Command-Comma on your keyboard. Click on the Accounts tab at the top, and then do the same thing as above – check off your phone number and the same email address you checked off on your iPhone or iPad.
If you’ve done all of the above, you might need to restart Messages. Hop into Settings on your iPhone and then turn iMessage OFF with the top toggle switch there. Turn it ON again after a few seconds and see if that takes care of things.
If all goes well, you’ll be starting and continuing iMessage conversations from all your devices.
Via: Gotta Be Mobile