Pretty sure I haven't run into a message that already deals with this issue. Basically I have an SE that I kept on 9.0 until ios12 came out. It synced with my mac on High Sierra with no issues. After I switched to 12, it quit syncing with my mac. My imessages on my mac are from 9/17/18 and no later than that. I've upgraded to Mojave in the meantime, logged out of imessages and logged back in, but nothing seems to work to get it to "see" that I have had plenty of new messages received and sent since that day. I'm pretty sure I didn't turn anything off/on when upgrading to 12, but it is possible something was changed and I never activated it. Anyone else have this issue and figured out what the trick is? Thanks!