"QUITTING DEVONTHINK Completing synchronization" forever? (DevonThink 4)

Your databases are not in Dropbox, locally or online. This is all discussed in the In & Out > Sync Explained section of the built-in Help and manual.

How did you set up the new Mac, e.g., via Migration Assistant?

I will definitely read that, and thanks.

I am making notes on my laptop’s DEVONthink, waiting a bit, and they appear on my desktop’s DEVONthink. I don’t know HOW it works, but there it is.

Should I INSTALL ADD-ONS? (PDF Services, etc.)?

I still don’t know what “DEVONthink would like to access it’s own folder Apps>DEVONthink Packet Synch inside your Dropbox” means.

My databases are all in a “Databases” folder on my desktop hard drive. I assume they will synch from there.

Remember also the notice I got many times: “DEVONthink Sync would like access to its own folder, App> DEVONthink Packet Synch, inside your Dropbox. Learn More.”

Sorry to be so fragmented - was working and fending off deadlines in between!

Almost forgot - I think I did use Migration Assistant to set up the new Mac (I do what Apple tells me)

Almost forgot - I think I did use Migration Assistant to set up the new Mac (I do what Apple tells me)

So your database(s) should have been migrated too.

Remember also the notice I got many times: “DEVONthink Sync would like access to its own folder, App> DEVONthink Packet Synch, inside your Dropbox. Learn More.”

No, you should not be getting this message as you shouldn’t have that folder on your Mac.
Read the Sync: Dropbox section in the In & Out chapter as this is also covered there.