Can anyone help me... Orbi RBK762S will not connect to internet

What is the Mfr and model# of the Internet Service Providers modem/ONT the NG router is connected too?
Be sure your using a good quality LAN cable between the modem and router. CAT6 is recommended. 

 

Check with the ISP to see if they require any WAN side configurations, like Static or PPPoE. 

 

Has a power off for 1 minute then back ON with the ISP modem and router been performed?
Be sure to restart your network in this sequence:
Turn off and unplug modem.
Turn off router and computers.
Plug in and turn on modem. Wait 2 minutes for it to connect.
Turn on the router and wait 2 minutes for it to connect.
Turn on computers and rest of network.

The Sky supported device does more, in some aspects much more than a plain Ethernet connected DHCP WAN router can do.

 

Your ISP does require MER (DHCP Option 60/61) for Sky FTTC in the UK to start with connecting third-party routers like the Orbi. Sometimes, it's even required to duplicate the original router MAC address. 

 

Well possible, the Sky supplied CPE (customer premise equipment) device must remain in place, for example to provide POTS phone port.