Stopped working

> Model: WNDR3400v2|N600 Wireless Dual Band Router

   Firmware version?  Connected to what?

> Stopped working

   Not a useful problem description.  It does not say what you did.  It
does not say what happened when you did it.  As usual, showing actual
actions (commands) with their actual results (error messages, LED
indicators, ...) can be more helpful than vague descriptions or
interpretations.  Any actual information might be more helpful than
"Stopped working"

   Visit http://netgear.com/support , put in your model number, and look
for Documentation.  Get the User Manual (at least).  Read.  Look for the
LED descriptions and "Troubleshoot".  Further reading might not hurt,
either.