New Xfinity Modem Does Not Allow Connections Outside Xfinity website and some Google sites

It seems this issue has occurred previously to others, see: https://forums.xfinity.com/conversations/your-home-network/only-access-to-google-and-youtube-some-devices-no-internet-even-though-it-shows-connects-cannot-connect-nest-ring-security/620319cee5fd17166fe51399

We recently needed to change routers (previously and currently supplied by Xfinity) after our last one was fried in a lightning storm. Initially everything went well, but then we realized the only sites the new modem would allow connection to are the Xfinity website (not this forum site mind you), Wikipedia, Facebook, Instagram, and some Google sites including Gmail and YouTube. No other websites or apps will connect and eventually give the error “This can’t be reached”. Level 1 support could not assist and the next level has yet to respond.

Edit: Some other websites found to be working such as Spotify web player, Genius Lyrics, LinkedIn, annd Amazon.

Some websites not working include Twitch, Reddit, Discord, Steam, and most online gaming apps.

We have reactivated the router, reset it, unplugged it/plugged it back, tried the automatic diagnosis through the Xfinity Assistant, and nothing seems to work. Oddly, testing the modem speeds in the Xfinity app generates an error of 0mbs and breaks the test.

This is issue occurs across all our devices, including my iPhone using WiFi, my windows computer using Ethernet, and my roommates windows computer using WiFi. 

Has here been a solution to this?