Do you have the "unsupported" MRV(multi-room viewing)? I ask only because you mentioned none of your receivers were showing up as networked. First,go to info & test & run the system test to see where you stand,or go to network set-up & run that test. What is most likely wrong is that you have the old IP Address from the old modem still on your receivers. You need to do a reboot(that helped me) to get a new IP Address from your new receiver. I'll give you an example,I have a Netgear Router with an address of 192.168.0.1 for AT&T DSL. the first 7 numbers(192.168.0) of your IP Address have to correspond with your router. Basically,just reboot your receivers(all of them) & then check again for network connection.
Never mind about the multiroom viewing question,just try everything I said after that question.