Deauthorization - macOS Catalina

When I had to change to my new computer, ADE no longer worked. I upgraded to ADE 4.5 but it wouldn't accept my books when I tried to transfer them from my Downloads folder to ADE in order to download them onto my Kobo. The first problem was my old ID - I no longer used that email address (the provider has gone out of business) and I couldn't remember the password I had used! I created a new ID using my current email address and Adobe deleted my old ID. HOWEVER, my computer still recognizes my OLD ID and I can't deauthorize it because I don't know the password! And I can't authorize my computer with my new ID because that option under HELP is greyed out! Can somebody please tell me how to get around this?