This error appears to be a permissions issue that most commonly occurred when customers upgraded their PC to Windows 10. But it does rarely affect Mac users too.

The solution for PC users is fairly simple. Before opening the URL_Link.acsm file instead right click on the shortcut to Adobe Digital Editions (ADE) and select "Run as administrator". This seems to resolve the permissions issue. If this does not work please check you have the latest version of ADE installed and update if possible. Then make sure ADE is not being blocked by your firewall.

Unfortunately we have yet to determine a similar fix for Mac users. Please contact our support team, quoting the error message and the affected ebook (and the format). We will try reimporting the ebook into our fulfillment server. If this does not work we would then ask you try uninstalling and reinstalling ADE.