Comcast has changed your mode to G/N instead of B/G/N. It doesn't make sense that it's not working, as your Roku supports both G and N mode. But for some unknown reason there are some cable modems that require the mode to be set to B/G/N.
The WiFi name (SSID) has nothing to do with it. You have to change the 2.4 GHz radio mode. And unfortunately, if you are renting your modem from Comcast you will not be able to change it yourself. I argued with their support for close to six months trying to get control of those settings, and I finally gave up and placed the Comcast Gateway modem in bridge mode and installed my own router instead. That was the only way I could have complete control of all my WiFi settings.
Since it sounds like you are already using your own router, you should be able to change the settings. that also means my first paragraph is probably inaccurate. The Netgear router is where you will find the settings I'm referring to, not in the Arris modem. Since I've never heard of Comcast providing a Netgear router, I'm assuming it's yours and you have complete control of the settings. I'm hoping you have the Arris modem in bridge mode, and you are not running a double router configuration. That usually causes connection problems with some Internet sites. But if the Arris is not in bridge mode, then you likely have two different wireless access points that are physically located near each other. That too is not a good idea, as they would be interfering with each other, even if they are using different channels.
Dan
Roku Community Streaming Expert
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