C3700-100NAS Unable to access IPv4 addresses

I used my device a six months ago with Comcast and it functioned properly, at that time, however the 300GB cap was very limiting for me so I switched to a hotspot with my mobile provider. Fast-forward six months the Comcast cap has been raised so I signed back up and now the device is not properly connecting to most websites. The commonality I could find was that these were big name web sites, and upon further research the actual commonality is that these sites (*.google.com; facebook.com; youtube.com) all support IPv6 only connections. Digging deeper I was able to discover that even with manual DNS servers (8.8.8.8) I am unable to even ping sites that support IPv4 only.

I was able to get a Comcast tech to install a temporary modem/router for me to use while I figure this out. As this will eventually cost me an extra $10/month, though I'd like to get the problem sorted out. I'd be happy to help in any way I can, but does anyone have any ideas other than buying a new router.

Thanks

P.S. C3700-100NAS running firmware version 2.02.08