Hi,
I would like to inform you that de-authorizing and re-authorizing ADE with the suggested steps should fix the issue.
If still facing the same issue, you may check the Adobe Id used to currently authorize Adobe digital Editions is correct or not. Make sure you have authorized ADE with the same Adobe Id/Vendor Id to which your eBook has been authorized/tied with.
If everything is correct with the Adobe Id/Vendor Id, then I would suggest you to contact your eBook provider and ask them to reset the activation for the eBook and provide you a new acsm link to download the eBook and that should solve the problem.
You may also try to download the sample books from the following link and see if that works- http://www.adobe.com/in/solutions/ebook/digital-editions%2…
Regards,
Ajit