ADE sometimes gets registrations confused and half registered.
Probably worth deregistering and re-registering.
To de-register the computer, ctrl-shift-D to ADE (cmd-shift-D on Mac), restart ADE, and then reregister.
That may well be enough, but if needed:
to de-register the device, ctrl-shift-E to ADE (cmd-shift-E on Mac) with the device plugged in, restart ADE, and then reregister.
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There are also bugs in ADE2.0 that mean using it with some eReaders goes OK with most books, but not with Overdrive library books.
My Sony PRS-350 is an example. The only solution I found was to revert to ADE 1.7.2.
(Quite a few other bugs in ADE2.0 as well).