Authorize new device for books purchased from closed vendor Books on Board

Yes, I used the same ID on my new computer and the downloaded ADE authorized the books that Ihad  purchased from Amazon with no problem. The problem is that ADE refused to authorized only the books I purchased from the now closed Books-on-Board because that vendor is no longer on the approved list. I paid for these books and moved these e-books from my old computer, which was authorized to open them, to the new computer. How can I get ADE to authorize on my new computer those books purchased from the vendor that is no longer in business? HELP!