Summary of HW reset button usage before I tell my story. All actions described are with switch already powered on and running.
- Reboot: push and release (not tested, presumed)
- Password Reset: push and hold for 5 seconds
- Factory Reset: push and hold for 10 seconds
Unfortunately in my case I had a useless switch for 3 or 4 days because I could not find this information ANYWHERE online. I raised a support ticket, and Tim from QNAP Support got back to me within ~24 hours with the information I needed. I successfully performed the HW factory reset procedure and was back in business.
After getting access to the switch again, I actually noticed the information I've documented here on the use of the HW reset button is shown on the web admin interface on the System Settings | Backup & Restore tab. Honestly it is completely useless to document how to do these things (which require access to the switch admin pages) when the reason you need this info is because you don't have access to the switch admin pages.
QNAP Support: if you're reading this please do two things.
- Setup a forum category for your excellent switches
- Add the information about the HW reset button in the print/PDF documentation