Yes thanks, @frmoses , perfect sense. I will have another go.
I did get it working via iCloud (CloudKit) which works well, but I would rather use Dropbox.
@Bob_h ā Iām a relatively new DT3 Pro user myself, who syncs DT3 <ā> DTTG via Dropbox. I would highly recommend reading and following, step by step, the instructions on setting up sync stores in Dropbox from the Joe Kissel Take Control of Devonthink 3 book (which is free, at DEVONtechnologies | Handbooks and Extras) . I used those instructions to set up my Dropbox sync stores, and found them clear and very helpful to follow.
HTH, and best wishes with your family situation.