unable to open book on eReader

this started late last week , I download a book to my eReader from my computer in ADE

it downloads okay, but when i go to open it, it does not open

i get the message , that my eReader is not authorized to open this book,  i have tried all of the logical things to do,

deauthorized it both in my computer and in my ereader, re- authorized both and it still does not work/???