Internet keeps dropping out

Looking at other forum threads here I can see that this is a persistent problem for Cox customers. 

For well over a year, this has been happening to me.  For 18 years prior, I never had to reset my modem and router.  When the problem started up over a year ago, I replaced my modem and router with new state of the art Cox approved hardware.  No help whatsoever.  Same problem, same error message from Windows Network Diagnostics:

"Ethernet" doesn't have a valid IP configuration 

The default gateway is not available 

This problem occurs even when the computer is shutdown (I know the internet is down because  my Wi-Fi quits working)

Calls to tech support are a waste of time.  I don't need to be told how to reset my modem and router since I have been doing it about 10 times a day for more than a year.

Had a Cox tech come out a while back.  He did some tests and replaced some connections.  My internet dropped out within an hour after his departure.