Edited to add:
Please ignore! It's working! Apparently my trial file was a bad choice (improper file name).
I just set up a Netgear wndr3400v.1 with usb port. v.1.28 Shibby.
I've enabled file sharing under usb support, and the 2TB drive is mounted.
I can access it from my pc and a wdtv live, can play files from it, and add files via copy and paste.
When I set the path in Sabnzbd and Sonarr, my downloaded files just vanish. No error messages of any kind. Files aren't written to the drive.
I've tried it with the HDD mapped as a network drive, and added the direct path, but can't get it to work.
Do I have to do anything further under "File sharing"? Auto sharing is enabled, no password.
Maybe I am using the wrong path? Would really appreciate some help to get this working.