QNAP to tape drive backup

Hi,

I'm trying to backup shared folders on my QNAP TS-459 Pro ii to LTO tape with Symantec Backup Exec 2014.

I can browse to the folder and see the files in SBE and from Windows Explorer with admin credentials supplied, but the test and backup job keep failing with:

Remote Agent not detected on marnas1.marriott.local. The logon account that was provided does not have valid credentials. Ensure that the user name and password are correct, and then try again.

This NAS runs Samba OS, so RAWS won't work. Can't get Linux agent to work either.

No NDMP options on the NAS.

Is it possible to actually backup from this NAS to Tape or am I just chasing my own tail?