I followed these steps:
On your iphone:
1) Go to Settings - Messages app – Preferences – uncheck iMessage on icloud and Forward Messages to my Mac.
2) Sign out of your Apple ID account
3) Sign back in with your Apple ID & password
4) Go back to Settings - Messages app - Preferences - enable iMessage on icloud and Forward Messages again.
5) Rebooted Mac...SUCCESS!
DetroitChango
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