CM600 won't register MAC address with RCN

Hi!  I bought a new CM600 yesterday, hooked it up and contacted RCN to register my new modem.  After an hour on the phone and multiple power cycles they were not able to get the modem to register on the network and told me the modem must be broken and that this is a common problem.  I'm skeptical and want to try again but I am wondering if anyone has any recommendations on how I might talk through it with the on-line rep.  I was a little surprised that I had the same rep on the phone for the sale of my service upgrade as well as for registering my modem.  For each cycle we waited 10-15 minutes for it to register.  Is it possible we should have waited a bit longer?

 

I could connect to the modem via 192.168.100.1 and could see the logs but the rep was not interested in that information.

 

They tried to register first with a 50Mbps connection as well as with my desired 250Mbps upgrade.

 

Thanks for the help!