[stumped]

update: well calibre box just works . installed to new tablet & it immediately found my dropbox library - I did not even need to go through any auth process!. ( and the dropbox app is not installed on this device ).

on the one hand, this is good as it shows that 3rd party apps CAN still get at dropbox.
but ion the other hand - whatever happened to dropbox security though- maybe its read only and calibre library only but still ? how did it know which of my several dropbox accounts has the library. it not linked to my gmail which is all the tablet shoudl be aware of- i had already linked moon to dropbox thouh so maybe it is piggy backing on that ( but I thoguht dropbox auth was per app, not for any app on a device ? )
anyway, I have nothing to hide in there so I will not fret too much. I might put calibrebox onto my phone, which has no reader apps and has never linked to to dropbox, just to re-observe the auth - or lack of auth process again.

calibrebox is a one trick pony though - it will connect to cloud storage options but not to calibre content server, so I guess I run this and CC side by side for now and point them both at same folder to download to

i bought the pro version to support the developer