ADT monitoring issue

I use ADT for home monitoring.  2 weeks ago, the ADT gateway showed no internet connection.  Wifi for other devices had been working.  Only the ADT gateway requires internet connection.  An ADT service came to diagnose the problem.  He confirmed the gateway was not getting internet connection.  Earlier this week, we had a new ADT gateway delivered.  Same problem persisted -- no internet.  We had the internet modem for almost 10 years.  Before we get a new modem, is there anything Comcast can assist to troubleshoot the problem?