Server Can not take back up

Hi, 

I am running windows server 2012 r2. Currently I m trying to take back from my server to my nas device. NAS device is connected by iSCSI. when i trying to take back up, i am getting this error.

Error :The backup rperation of the volume did not start.

Status:Backup failed to complete. The volume change journal is being deleted.

Please help me to rectify this issue.

abusaleh