It's nice to have some sort of answer at least... Unfortunately, I can't use a cellphone's hotspot, because I don't have one (I know, that's a little weird by today's standards .x.). I've had the issue for... well, two or three days or more, although the Comcast tech visit was a week ago and I was taking a short break, so I didn't notice 'til just recent.
I hope it goes away... I'd hate to be stuck locked out of FH forever. .n.
Oh hey. I just noticed something. It doesn't fix my problem, exactly, but it is a workaround. Comcast has this hotspot thing they do. I tried connecting to that instead and that allows me to connect?? Maybe it really is the modem. Interesting. Needless to say, the main problem isn't fixed, still, because it's not a permanent solution, but it is something. Thanks for reminding me that the hotspot was an option, Hakumi.
EDIT: Curiously, my second post, posted under the hotspot, has a different IP address from that first post.