What to do if firmware update failed
1. Please go to QTS-->Control Panel-->System Settings-->System Logs to check the event log. And you can refer to below table of error code to identify the issue.
2. Please try to reboot the NAS and do the firmware update again.
3. If it still failed to update the firmware, you can do the manual firmware update with below link. (go to step 4 if you are not familiar with Linux)
http://wiki.qnap.com/wiki/Manually_Updating_Firmware
4. Contact QNAP support for the assistant.