I have the same problem as many other users. Entitle Ebook Subscription was shut down in 2015, and now I am no longer able to access the ebooks that I have purchased. I have the ebook files in my ADE library but am unable to open them due to the vendor ID no longer working. Many users have inquired about this judging by the discussions I have found. However, no one has answered. How can I switch from Entitle DRM to Adobe DRM?? Or is there some other way around this?? Please help me!!!
Unfortunately, when a VendorID service shuts down, the account will be lost and subsequently access to the books purchased with this account is lost as well. The only option going forward is to create an AdobeID account and make sure to purchase your books with this account. You'll know that going forward your books won't be bound to a VendorID account that has the potential to shutdown without any recourse.