Contact Adobe Technical Support - they can help you clean up your devices
and reset the counter.
I have a similar problem. I asked to Adobe Technical support (through a chat on adobe web site) and they told me that Adobe doesn't give support on chat or telephone for Adobe Digital Edition because it is a free application. As a consequence, they suggested me to ask here.
Does anybod had a similar issue? How can I remove ADE authorization from a device I don't have with me?