Issues with firmware V5.21(AAZF.7) on NAS326

Skippy

It appears the system I have is unable to reset to factory defaults, heard the 3 beeps, web interface still not working.  How do you rewrite the firmware to the system board? 

Sapphire23

Try running this file via ssh access:
/usr/local/btn/reset_and_reboot.sh

Or you can make a manual firmware upgrade: control / fw upgrade
https://il.zyxel.com/support/download_landing/product/nas326_13.shtml?c=gb&l=en&pid=20150327120001&tab=Firmware&pname=NAS326