Wifi issue with accessing secure websites

HELP!! This is now the 2nd time this issue has come up.  We lost access to any secured sites, such as Netflix, Hulu, any banking or work sites, with no changes to our settings or modem/router.  Been through 6 xfinity chat reps, and no one can help.  Chatgpt suggested changing the DNS network to google, but there is no way to do that for the modem/router, the option is a view, and the primary DNS is 75.75.75.75  I changed it on my PC to 8.8.8.8, and my TV, but that didn't help the issue.  I have a few devices connected to the wifi, and think that the ones that are connected to the xfinity pod can get to the secured sites, but not the ones connected to the gateway modem/router.  Did many resets and restarts with no change.  There is no way to automatically connect to just the pod, looks like it just picks up the device randomly?? My TV won't is connected to the router and won't connect to any streaming services.  Any suggestions would be great, thanks so much!