I have it working after a pause of 24 hrs.
When the error first occured I tried authorising with Aldiko, and failed. I tried Aldiko after the 24 hour pause, and it worked; so I tried entering the registration data in Overdrive, and it worked.
It's DRM. It's Adobe. Who knows? Mastering these black arts will forever remain a mystery.
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I don't mind the Overdrive reader, I quite like the Aldiko reader. I must look at the Bluefire reader.
I also find Overdrive Read on my Samsung ARM Chromebook quite good. In laptop (landscape) mode the viewing area is big enough in full screen mode. I can rotate the screen and use the whole 11.5" portrait display for the big print-big book look.
A Lenovo Joga with its bend-right-back keyboard would be good for that.