erase computer authorization

I am trying to import books into Adobe Digital Editions.  However, when I do this, I keep getting the message "Unable to download, Error getting license.  License server communication problem:  E_ACT_NOT_READY".  So I followed directions and was told to erase the computer authorization.  However, when I tried to do this, the email account that shows up I no longer have access to and I don't remember the password for that account.  How do I erase the computer authorization in this case?

My operating system:  OS X 10.9.5

My web browser and version:  Firefox 40.0.3

Flash Player version:  18.0.0.232