This works on a Mac, but finding the activation .dat file on an IBM then deleting will be a different way, but the successful outcome will be the same.
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.
Thank you. Following your suggestion and looking up what it meant in Win 10 I was able to find this:
If the deauthorization process doesn't work try this:
Choose start > Run
Type regedit and press Enter
Locate registry key on left panel
Select Adept key
Enter name and location for back up registry key, click save
Right click Adept key and Delete
Confirm, click OK
Open Adobe Digital Editions and reauthorize