iMessage on my mac says every contact is not registered with iMessage

This fixed it for me. http://osxdaily.com/2012/08/09/fix-imessage-syncing-between-mac-ios/

This link fully help you

http://timeinpixels.com/2014/10/sms-relay-ios-8-1-yosemite-registered-imessage/

The answers supplied by Ralph do not work and are a clear case of overkill. I tried the ones suggested with no positive results.

Thank you. Unfortunately, my problem is with Google's Hangouts talking to iMessage, which is different than text messages. I do have regular text message forwarding working just fine.

Ejeide, thanks. Your fix worked for me. I was logged in under my AIM account rather than my apple ID. When I changed that, iMessages came back to life. For those who want to try this on your Mac, open Messages Preferences and look at Accounts. Make sure you are signed in with your customary Apple ID. For some reason I wasn't. Log in with the Apple ID and (fingers crossed) it should work. (I recognize there are others with more elaborate troubles; I just wanted to underscore that this simple fix appears to resolve the trouble for some of us.)

I'm having trouble with this since I updated iOS to El Capitan.

Whoops, sorry, had me upgrade from Yosemite to El Capitan. So all the software is as up to date as it can get on phone and Mac now. No luck.

Hi

I can't see the "verified" indicator or activate the process anywhere on my account information anymore.

This is so frustrating, WhatApp does this without any issues. 😠

I have just worked this out! contacts mobile numbers need to start with the area code e.g. +44 71234 56789

This has worked for me anyway, good luck! 🙂

You need to click on "Messages" top left, "Preferencess...", "Accounts". Clicks on you iMessage id in the accounts box, then enter in your password and sign in. That fixed it for me.