@thisistheslam: I made an account just to come thank you for this.
My console did the exact same thing about two weeks ago when I came home from work. And because I was so out of sorts from work, after otherwise unplugging and resetting everything about 10 times and getting absurdly frustrated with the OS basically smiling and shrugging at me, I made the glorious mistake of trying to speak with Microsoft's live tech support chat.
Don't do that. It's a bad idea.
Once we got through the fun of me explaining the problem as specifically as possible and then being asked "Okay so if I understand correctly, you're having a problem with your controller connecting?" I was told (probably just pulled arbitrarily out of a list of help topics) that clearly the only solution was to do a factory reset, with the same incredibly competent expert assuring me that, no, my data would be fine. Fortunately I decided to not trust that (and also not wait for 475gb of games to reinstall) and opted to buy an ethernet cable instead. And then I didn't do that either, because while they're $12 on Amazon for the 50ft cord I would have needed to run the damn thing downstairs and across my entire house, they're $30 in retail for some reason? So then I got too mad and lazy to order one lol
And then on a whim I went digging through forums again and finally found your reply here and I can't thank you enough. Never even occurred to me that I should just treat it like a frozen computer and that it would treat a kill/boot from the console differently than the controller.
And for anybody less technical who's up there suggesting "did u restart ur router," what's essentially happening is that the hard reboot forces the machine to realize "oh no, I turned off because something went wrong, better make sure everything's okay!" as opposed to "oh lol I've been turned off and back on again, let's make sure all the settings stay the for next time."