[stumped]

but I am not testing the Kobo ecosystem or the Kobo claims
I am testing the overdrive system and the claims made for overdrive

summary: overdrive installed on 2 tablets. book checked out of library using overdrive app and credentials which downloads an epub to android file system.
that book is readable on both devices in overdrive but not in aldiko or bookari , though both those apps claim to support overdrive DRM
book cannot now be checked out to ADE on PC becaus e I get an already fulfilled by another user error
there is nothing in overdrive's blurb about such limitations applying
it may well be that with a kobo KA1 I can bypass the whole mess, but that's a different challenge. Here I am just trying to understand what can / cannot be done with overdrive and/or adobe and my library membership on the various devices I already own.
[ i may test the route of login to library with library card, checkout a book in to ADe with my adobe ID, then push that onto tablets, try to open it with the reader apps that have my adobe ID, but that's a tortuous route. I'd be doing it only to see what happens, but as a viable workplan for actual reading. I could also try login to library with browser on tablet and see it i can get an acsm file to download to tablet that way. then use that in aldiko/bookari- but i suspect it will not work. everything I read says i need to go via ADE to borrow books , or i need to use the overdrive system]