Netgear EX6400v2 power light stays amber and won't connect

[AcePilot2002]

My EX6400v2 extender was paired with / connected to an ARRIS DG3450 cable modem/router installed by my local cable tv/ISP provider. It would occasionally have intermittent network connection drops but usually not a problem. However, it stopped working yesterday and does not want to seem to reconnect to the wifi network again. Instead, the power light now stays a solid amber color. All other lights on the extender are a dull amber/yellow color to the extent any 'light' is visible in them.

I have tried unplugging the extender for several minutes and then plugging it back in but no change occurs.  I also have tried doing the factory reset with a paper clip but the factory reset does not seem to take.  The power light remains a solid amber and does not start blinking despite the reset button being pushed for varying amounts of time up to and including one minute.

Attempting to log into the extender via http://mywifiext on my Windows 10 computer is unsuccessful.  My web browser (Microsoft Edge) tells me that the page cannot be reached.

Are there any remaining potential solutions available that I haven't tried yet?  Or is the device 'bricked' and trash? The device is less than 1.5 years old.

Thank you.

[plemans]

You can try recovering it with tftp or nmrpflash.
are you on windows? if so, follow this guide
https://kb.netgear.com/000059634/How-to-upload-firmware-to-a-NETGEAR-router-using-Windows-TFTP
just make sure you enable tftp
https://www.thewindowsclub.com/enable-tftp-windows-10

and here's a video walk through using a tftp client. Use the built in one for windows 10 though. the video is more of an example of how its done.
https://www.youtube.com/watch?v=R9DLrLQrpaw

and if that doesn't work, you can try using nmrpflash
https://github.com/jclehner/nmrpflash

[AcePilot2002]

I am on Windows 10.  Can I try / use that solution with the range extender?  I ask because the link you provided says that it is for uploading firmware to a Netgear router (not extender). 

Does it matter that I am using an ARRIS modem/router for the Wifi network?

Thank you.

[plemans]

It won't matter. The video I posted is even done on a extender.

[AcePilot2002]

Thank you.  I will try that and see what happens.

[AcePilot2002]

Unfortunately when I attempt to follow the command prompt option for uploading the firmware from my computer, the response I get after hitting enter on the tftp command is the following:  

Connect request failed

When I tried using the tftp windows client option following the instructions from this website: 

How do I upload firmware to my NETGEAR router using a TFTP client on Microsoft Windows? | Answer | N...

it again appears to just 'hang' after I hit the 'put' command, even though I leave it alone for nearly 10 minutes.  Instead the power light continues to remain a solid amber/orange color.

Is the extender device irretrievably 'bricked' / wrecked?  Any other thoughts/suggestions would be deeply appreciated.

[plemans]

tftp and nmrpflash are sensitive to timings. (try them both). 

Its taken several times before with a couple I had to get them to go through. 

don't give up after one attempt