My R7850 ac3000 Router wont let me change SSID or password

My Router is a Netgear Tri-Band 6x Model R7850 was working fine until yesterday.

It kept telling me to NOT CONNECTED TO ROUTER.   Checked everything and all was connected but gives error SITE CANT BE REACHED. Tried to access router through Nighthawk app but said router not set up.

So I went through all the set up and it defaulted to the SSID and Password on the router so I tried to change it but when I went to save it said IT COULD NOT ACCESS ROUTER to save.  Went through the whole process again but left everything at default (SSID AND PASSWORD)  it works and I can use Nighthawk app but now cant change Admin Password as old wont work or change SSID and Password and it wont save but gives error. I have done Factory reset 3 times but no change. 

The Router runs off my Frontier NVG468MQ with windows 10 home 64 bit HP Envey 700-216 amd elite quad-core A10=6700 Accellerated Processor, 12 gb ddr3 system memory 2tb hard drive.

Tried everything I could think of to fix but still stuck with the same problem not able to change SSID and password  or access router as it asked for recovery answers and say wrong answers inputed try again.  Just bought this last early last year and may have to buy another if this cant be fixed. Any Help greatly appreciated