iMessage no longer syncing since updating to El Capitan
I use iMessage on my iMac, MacBook Air, iPhone and iPad. All was working well until I updated the Macs to El Capitan. Now, the messages do no sync reliably.
I have attempted to logout of iCloud on both devices. As an example, my MacBook has my last text at 11AM, while I have numerous texts on iPhone several hours later.
MacBook Air (13-inch Mid 2012), OS X El Capitan (10.11)