[stumped]

So I decided to see what I could do with overdrive on my Samsung tablet.

And I am stuck...
I logged in to Overdrive app, on the tablet gave it my library card stuff, and checked out an epub... it downloaded and I can read it in the overdrive app, but i am not impressed with the reader app...
I try to open the downloaded epub in Moon reader but it is protected so that fails as expected.
Then I recall that bookari has some drm handling ability. I launch bookari, give it my overdrive account info, then try to open the downloaded book in bookari. No joy some sort of adept core error message. I dig out my adobe ID credentials and give them to bookari also. Still no joy.
What am I missing.
Overdrive app says it has activated or authorised by device.
And bookari say it has my overdrive credentials so why can it not read the borrowed book. Is overdrive the only app that can read it on this device. I don't recall seeing that restriction written down anywhere. And why does bookari bother to accept my overdrive credentials if it does not acually know how to use them