Can't load any ebook

Hi. I'd like your support with the following issue: I had to change my computer and now that I installed Adobe Digital Editions, I have the following error and I can't open any of my ebooks.

"You have reached the maximum number of devices allowed by your ID. This computer can't be authorized with your ID because it has reached the maximum number of computers of devices that are allowed with the same ID."

How can I solved this issue? I guess there is a way to deactivate some of the devices already authorized, but don't know how because in my account I haven't purchased any software.