This indicates a mismatch in the protocol used to transfer attachments between the NotfiyLink device client and server. This protocol was changed between the NotifyLink Enterprise Server versions 4.5 and 4.6. If both the device client and server are not using the same protocol the attachment download will fail with this message.

This can occur if the message(s) associated with the attachments were processed by NotifyLink prior to upgrading your NotifyLink Enterprise Server from version 4.5 to 4.6. Due to the protocol change, any attachments associated with these messages will not be downloadable. The only solution to this scenario would be to have the messages resent after the NotifyLink Enterprise Server upgrade was complete.

This can also occur if your device was registered to a NotifyLink Enterprise Server version 4.5 that was upgraded to 4.6 and your account was not resynchronized after the upgrade. In this case the device client is unaware that the server was upgraded from 4.5 to 4.6 and therefore will continue to use the old version of the protocol while the server is using the new version. The solution to this scenario requires you to send synchronization messages to the device via the Administrator web console or the Client web console.

Check to make sure that you have the latest version of the NotifyLink device software as well as the Notify Core Library component that the NotifyLink application is dependent on. There have been updates deployed to both of these components specifically to fix problems with downloading attachments that will result in this type of exception.