iMessages & SMS not syncing on iMac

Because of a corruption I had to create a new user on my iMac and move all of my files etc. across. The new user account works just fine except for Messages. All the pre-existing messages that are on my MB Pro, iPad and iPhone are not syncing to the Mac. I've checked the Apple ID is the same on all 3, have logged out and logged in on all 3, checked that the addresses are all enabled, sent messages from all 3 devices, and tried Sync Now on the iMac. The only messages, SMS or iMessages, that I see on the iMac are the ones sent or received since the User changeover. All of my messages are on the MB Pro, iPad and iPhone. I'm at a loss. Is there a way to force or copy over the message history from any of these devices? How about moving them from the old corrupted user account? Some other solution? It's driving me nuts.