Synchronizing Messages Across Devices

I have a new MBP16 M3 system that was set up using Migration from my older MBP16 M1. Everything has worked fine except for Messages. I use Message mostly on my iPhone 14, but copies of my incoming and outgoing messages also showed up immediatly on my Mac Studio and my (old) MBP16 which was very convenient if I wanted update the messages on those systems. Now the new MBP16 M3 system doesn’t show the new messages at all. (Old messages were shown after the setup - but any new updates are missing.) In one case, the missing messages showed up a couple of days late, but I am still missing lots of messages. I have iCloud synch turned on for each of these devices - as far as I know, the new system configuration isn’t any different than the Studio or the old MBP. (Oh, the messages also show up on my iPad.). The big irritation is web sites that send login codes via messages - they don’t show up and of course the feature to plug in the codes doesn’t work.

Suggestions any one?

I’m usually hit by this when I add or replace a device. Here is the probable fix:

On your iPhone go to Settings>Messages>Text Message Forwarding and be sure it is turned on for the new device.

Messages sent via iMessage show up automatically, but this needs to be turned on so that SMS messages are properly handled.

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What do you have here on the phone?

But I will say that I have found the behavior confusing and inconsistent. I don’t know how the setting above interacts with cloud sync. I don’t know why there is a sync button at all; doesn’t iCloud sync on its own?

I’d love somebody to do a deep dive into how messaging syncs across Apple devices.

Something very similar has happened to me. Messages on my MBP occasionally likes to think I’m not logged in to iCloud, even though in system preferences it shows I am.

But then if I look in Messages I’ll see that for some reason I’m logged out of iCloud, but only in Messages. Then when I try to log back in from the screen in Messages preferences, I’ll get a nondescript error. A restart then fixes it.

I’ll also mention this often, but not always, seems to happen in conjunction with a series of pop up notifications asking me to enter my password for this or that Keychain related item.

Thanks! It wasn’t turned on for the new device.

David

Yes, as I mentioned, I did have some new messages show up (even when forwarding hadn’t been turned on). I am used to iCloud sync being slow. I have seen it for Safari bookmarks too. I turned off optimize Mac storage (the new MBP has a 2 TB SSD) and expected to have everything downloaded and synced. Nothing happened I had to manually select folders to get it to download to the new system.