Orbi Robust Smart Home Wi-Fi Tri-band Mesh Wi-Fi 6 System will not connect to provider’s modem

Not much to go off of.

What Orbi system model do you have? 

What Firmware version is currently loaded?
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. 

Has a power off for 1 minute then back ON with the ISP modem and router been performed since last update?
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.