Activating internet service with NETGEAR Cable Modem CM500: "Please check RF connection."

Hi, I am trying to activate xfinity internet using a netgear cable modem cm500. I am unable to connect to xfinity to activate, and when I connect the modem with an ethernet cable and log in to the modem, I get the error "Your modem is offline. Please check the RF connection." I would be grateful for any thoughts on how to address this. Thanks!