Digital Editions says, I've reached the maximum number of devices to transfer my library to.
But I'm quite sure that I use two Computers, two ebook readers and one mobile device. But it's not possible to activate Digital Editions on the mobile device.
So, is somwhere listed which devices I use already? Or is there a possibility to erase one of the used devices?
There is not proper webpage to view and manage authorized devices.
The only thing is to contact Adobe Live Chat: http://www.adobe.com/support/chat/ivrchat.html
They can reset all your authorizations, and then you must reauthorize any devices you still need.
(Unfortunately, Adobe haven’t got round to an admin website for viewing and editing authorizations.)
Some of the representatives haven't been properly trained and don't know what to do (and claim there is nothing they can do);
in that case the only way seems to be to give up that chat and try another session hoping for a properly trained representative.
If your problem is with another device using Overdrive, Bluefire, Aldiko or similar third party app, it is recommended not to mention that app when on the chat, just mention that you have run out of authorizations (E_ACT_TOO_MANY_ACTIVATIONS) . Thanks to AJP_Bear for that tip.