MR63 "Check Ethernet Cable" Nighthawk WiFi 6 Mesh Internet Router

Hello,

I got the Nightawk Mesh WiFi 6 MR60 router with the two satellites. When I plug it in and run the setup I get "Check your ethernet connection"

I'm plugging it into  at Cisco DPC3008 Docsis 3.0 modem from Spectrum (it's a bit of a dinosaur).

I checked that I'm plugged into the "Internet" port on the back of the router. I've rebooted and factory reset and it's still giving the same error. I waited on hold for over two hours to be hung up on when I finally got tech support. Hoping someone here can assist.

Thank you in advance!

-jeremy