site inaccessible from xfinity but not other carriers

I've been going round-and-round on this one with xfinity. 

7-9 days ago idrive.com became inaccessible via my xfinity/comcast internet connection. It is accessible via my cellular data carrier (AT&T) and if I access it via another carrier through a vpn. No other sites that I routinely use are affected. 

Does anyone have any suggestion on how I can either get xfinity to understand and register my problem report, or diagnose and address the problem on my own (if that is at all possible, which I doubt)?

Here's what I have done:

A traceroute to the site times-out at hop 20. Hop 19 is always the same (viawest.net) router. I've verified that the site is live by connecting using my cellular data carrier (AT&T), and by connecting via a vpn to another carrier and accesing the site. Over the past week I've been in contact with xfinity seven times. Most times the contact ends with an insistence that there must be a cable connection problem to my home (even though my internet connection to every other site is fine) and the desire to send a technician to my home to inspect the cable. Twice it has ended with a promise to escalate the report to the next level of technical support. Just to move things along, when xfinity wants to send an agent to my home I agree to the service visit, which xfinity schedules, and then cancels (on its own accord) in a text message several hours later. When the report is escalated I am told I will be contacted either in 10 minutes, or 1-2 days. In neither case did second-level technical support ever contact me back. In all cases when I try to contact xfinity again we go through the entire "Is your modem plugged in? Are the lights flashing? Can you disconnect the power, wait 20 seconds, and plug it back in? Is your internet working now? Can you disconnect the cable from the wall? Etc.", with the same response.