Orbi RBK20W will not connect to satellite only get white flashing light

What Firmware is currently loaded?
What is the Mfr and model# of the ISP modem the NG router is connected too?

What is the size of your home? Sq Ft?
What is the distance between the router and satellite(s)? 30 feet is recommended in between RBR and RBS to begin with depending upon building materials when wirelessly connected.

What channels are you using? Auto? Try setting manual channel 1, 6 or 11 on 2.4Ghz and any unused channel on 5Ghz.
Any Wifi Neighbors near by? If so, how many?

Try enabling Beamforming and MIMO(MIMO may or maynot be needed) and WMM. Under Advanced Tab/Advanced Settings/Wireless Settings

Try disabling the following and see:
Armor, Circle, Daisy Chain, Fast Roaming, IPv6 and Set 20/40Mhz Coexistence to 40Mhz only. Save settings and reboot the router and satellite(s).

Has a factory reset and setup from scratch been performed since last FW update? Power OFF The ISP modem for 30 seconds then back on then walk thru the setup wizard after doing a factory reset?

And you have done what to try to fix this?