Can't connect to Internet with Arris SB6190 after dropping cable

Too long of a story, but I finally decided to cut the cable and go streaming only.  After returning home after dropping off the TV boxes, I could not connect to the internet with my SB6190 that had been working perfectly.  I spent an hour with tech support (check connections, restart, reset...) and then had a service tech come out.  He could get internet with an Xfinity modem.  So, I bought a new SB6190 from Best Buy.  Exact same response, no connection to the internet.  I called Arris and they said it was a Comcast issue (very coincidental that it stopped after they changed my plan).  Spent another hour this morning with tech support, then had a service tech out again.  I ended up getting an Xfinity modem for the near term, to just get back in service.  I can't help but think something happened on the Comcast side from changing my plan from TV/Internet to Internet only.  I even took the modem to the box on the house to take all internal wiring potential out of the equation.  Same results.  Has anyone else had a similar issue?  I don't want to rent a modem from Comcast from now on.