PC, tablet, not even your AT&T phone when on WiFi?
The site stedi.org works fine through my AT&T phone. But I cannot access it via the XFINITY networjk.
I can reach the site fine from my end here in Northern N.J. Perhaps the results of a trace route to the site may reveal a clue ? Please post the output.
Good to hear. As I suspected, it looks like your previously Comcast assigned public / WAN IP address was being blocked by the site for some reason. When you spoofed a different MAC address, it forced their DHCP server to assign a different Public IP addy to your connection.