I'm having the same issue. I have two Roku devices in my house and both were working fine with my old Arris SB6141 DOCSIS 3.0 modem. I just replaced that modem with an Arris S33 DOCSIS 3.1 modem. After the modem switch the Roku's were working fine but because of some Xfinity glitch...I needed to reboot the S33 every couple of days. Therefore, I switched back to the SB6141 to get a stable internet connection. However, after switching back, the Roku's would not work properly and presented an "Internet Connection" error. Everything else worked fine with the old modem...only the Roku's presented a problem. After a bunch of troubleshooting, I reinstalled the S33 modem and the Roku's began working fine again.
How did the Roku's imprint to the DOCSIS 3.1 modem so I can't go back to DOCSIS 3.0? Is there something I can to to get the Roku's to again work with DOCSIS 3.0?
I gave up, rebuilt my entire network, and replaced the mesh wifi. Everything works now.
