I had the same problem on my Mac.You need to remove the activation.dat file from your system , then re authorise.
If you have a Mac, the following worked for me, compliments of bmorgan54 - if you have IBM, then some other means of removing the activation.dat file needs to be found. Thanks again to bmorgan54, after me not getting any useful help from the so called Adobe Help Line experts, only frustration.
A few months ago I changed my Adobe ID and password. Fast forward to now and I'm having the same prob as everyone else. Here's what worked for me:
1. Go to the Finder menu.
2. Hold down the Option key and select Go. This reveals the hidden user library.
3. Select Library.
4. Go to Application Support -> Adobe -> Digital Editions and delete the file named “activation.dat”
5. Now one can reauthorize Adobe Digital Editions.
I have a Dell lap top and run Windows- I can't find the "option key" or "go" key as it's not a Mac. Do you know how to do it for a common or garden Windows platform?
no, not really, but the file to delete is still the "activation.dat". do search for it using the search feature, even in any hidden files, it should be in the library (or hidden library ) files. Look through the answers to problems under the bmorgan54 name, as i think that he may have had an IBM method to find and delete this file.