E_ADEPT_DOCUMENT_TYPE_UNKNOWN from libreriaitaliana.it

I've bought an ebook from libreriaitaliana.it, and when opening the .acsm file, all it shows is the E_ADEPT_DOCUMENT_TYPE_UNKNOWN error. I thought it was a problem with the bookstore, but when speaking with them, nothing could fix the problem. I changed the account, downloaded the file multiple times, uninstalled and reinstalled ADE and even got a refund so I could buy the book again and the key would be different, but nothing has helped. I have bought a product I cannot access so I request help.