Nighthawk cannot factory reset after firmware update and reboot

Hi and thanks for the quick reply!

I have read so many threads and done so many things - only one worked just now so thought I would share the good news.

Solution was to connect via LAN with a Win10 laptop set at 192.168.1.10, subnet 255.255.255.0 and default gateway 192.168.1.1. 
From command line, set it to ping -t 192.168.1.1   - and reboot router. Make sure all is pinging fine and wait about 2-3 minutes. At this point, as with every other reboot - power light flashes amber as always.

Now, instead of using the TFTP2.exe software as per Netgear article (which did not ever work), I did the following:

In win10, control panel, add windows features - i added/installed TFTP (this is an OS component, not a third party program).
Once installed, I opened a Command Prompt with administrator rights.

I ran the following command: 

tftp -i 192.168.1.1 put R8000-V1.0.3.4_1.1.2.chk

(change the firmware file name to match the latest you downloaded and unzipped)

This then said transfer successful - and while it was doing it I noticed the power light stopped flashing and stayed solid amber (for the first time so knew something different happening). Router then rebooted a few times and I just left it until a few minutes later when all was up as normal, all lights regular color, and we were back to factory settings!!

Hope this helps!

Dave