Netgear r^400

For years I had

Integrated PoE (Power Over Ethernet) ports providing power to cameras and video connection to NVR

Ethernet connection from wall to the Netgear R6400 WAN

RJ45 from Netgear R6400 LAN port to Modem WAN

Laptop connected wireless to internet. (Windows 10)

2 days ago, error message, secure connection to router, no internet access.

Called cable company, not their equipment.

Reset modem & factory reset router - no change.

Changed connect setup to

RJ45 direct from router WAN to modem WAN - internet access but cameras not working.

Now only way to get cameras working with internet access is to keep new configuration & terminate NVR in Netgear AC750 WiFi Range Extender Model EX3800 

Any suggestions as to why the initial setup failed? I prefer that over having the Range Extender for this application.