Orbi RBR750 won't show any satellites

Wow, thats several revs back. No wonder. 

Ya if you can get to this RBS web page to upload v.2 FW from here:

https://community.netgear.com/t5/Orbi-WiFi-6-AX-and-WiFi-6E-AXE/New-RBR750-RBS750-Firmware-Version-4-6-8-2-Released/td-p/2217844/jump-to/first-unread-message

Load this version first on this RBS, Then do same on the other RBS, then update the RBR lastly. Once you update the RBR lastly, Power OFF the RBS and RBR for 1 minute then back ON with the RBR first, then RBS one at a time, they should connect. If not, you may need to factory reset the RBS and RBR and setup from scratch.