NIGHTHAWKK ac1900 I can't access router dashboard

> NIGHTHAWKK ac1900 [...]

   "AC1900" is a speed, not a model number.  Look for "Model" on the
product label.

   Connected to what?

   Visit http://netgear.com/support , put in your (actual) 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.

> [...] I can't access router dashboard

   "can't" is 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.