Authorized vendor ID issue

I purchased and downloaded an ebook from Booksamillion in July 2020. I was able to access it via Digital Editions as recently as January this year. Today, I tried to open it, but received a message saying that Authorization is needed. When I start the authorization process, the only vendor that is available to me is CloudLibrary. I cannot change it to Booksamillion, and I do not have a CloudLibrary account. How do I fix this so I can access this book?