Problem using Norton 360 Security to backup to WD Elements portable drive

Would anyone have had trouble with this. I have successfully backed up a Levono desktop but when I try doing the same with a HP Touchsmart 520-1010a I get the following error - “make sure the destination drive or device is connected and then try again”. Prior to starting the backup, the drive is showing as connected. Would be glad of any input

Are you able to copy and paste files into your hard drive in the same computer or use other backup applications?