no wifi connection

> nighthawk r6400v2

   Firmware version?  Connected to what?

> can connect via ethernet cable BUT NO WIFI can not connect table or
> laptop via wifi

   "can not" 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.

   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".  Pay particular attention to the
"WiFi On/Off button with LED".  Did you press it?  Further reading
might not hurt, either.

> 2. bought a brand new netgear to fix #1

   The non-psychics in your audience might be unable to guess what it is
or what you did with it.

> it had NO INTERNET AND NO WIFI (ax1800)

   "AX1800" is a speed, not a model number.  Look for "Model" on the
product label.  I'd guess that there's a User Manual for it, too.

> would someone PLEASE tell me what to do........

   You might try this radical concept which works for some people:

      https://en.wikipedia.org/wiki/RTFM

> it's not their products.

   Right.  Wired-good, wireless-bad is a local-to-you problem.

cisco modem to netgear router, 

i get internet via ethernet but no WIFI

the cox cable guy came in and pushed the ON wifi button, that i did not know was NOT A LIGHT, but a button that lights up

and all was fixed,

except now i have 2 alexas and one works and one says i have no wifi...........................