Separate the 2.4 GHz and the 5Ghz bands on your gateway then change the 5GHz band of your SSID to a different name, then try to connect. If successful you can change them back.
I am not a Comcast Employee. I am a Customer Expert volunteering my time to help other customers here in the Forums. We ask that you post publicly so people with similar questions may benefit from the conversation. Was your question answered? Mark the post as Best Answer!