I started having a strange problem with iMessage. I could get messages on my i-devices, or on my Mac, but not on both of them at once. Since I rely heavily on iMessage this was a problem. I figured out that if a message was sent from a Mac, I received it on my Mac and if sent from an i-device I received it on my i-devices. Since this started around the time iOS 7 was released I figured my problem might rest with iOS 7.
Sure enough, it was an easy fix. You have to tell your i-devices to accept messages.
Start by opening the Settings app on your i-device. Select Messages.
Clicking on Messages takes you to the Messages window.
Select Send & Receive and you get this window.
Under the heading “You can be reached by message at”, be sure you enter all the email addresses associated with your Mac addresses. For example, firstname.lastname@example.org, or email@example.com. This should solve your problem.
It solved my problem, hope it does the same for you.