This will log more detail to your system log, which can be viewed in /Applications/Utilities/Console.app.
After you’ve attempted the Sync, open Console, type “DEVONthink” in the filter field in the upper right-hand corner, and copy and paste ALL of the window’s contents into a new text document. Start a Support Ticket at our DEVONtechnologies Support Ticket System and attach the document to your reply. Thank you.