[stumped]

last update- then its back to the dark side. the legit options are a big broken mess
I go : library checkout -> ADE then copyteh epub to dropbox
NB the download to ade is fine ( I can read it in ADE and I can open it in calibre with help from alf)
from dropbox i export to downloads folder on tablet.
then I take each of bookari, Aldiko. i activate the tablet for my adobe ID in both apps and get OK - device activated.

but will the book open - Nope. Aldiko just says error. Bookari imports it but "open" leads to a "no tokens found" error .
the exact bookari message is
The document has expired W-ADEPT-CORE-NO-LOANS-TOKENS-FOUND

and just to prove the file was still ok at dropbox stage, i go ( on PC ) dropbox ->copy to desktop-> add to calibre . open - all good, thanks to Alf.

so the whole business of authorising android devices with adobe ID then sideloading the file(s) that are DRMd with that ID simply does not work, not for the apps I tried anyway. maybe it would/should work with a bought book but not a loaned book? - but I don't plan on researching that.