I am having the same problem, have been having this issue since around the 19th (4 days ago). Also have AT&T fiber and in the SE USA. Using an Asus Rog strix, if that matters. My partner has been able to log in though (he'll occasionally have the same error but not every single login attempt like I've had lately, and can sometimes get through). I've tried updating windows, restarting computer, clearing browser history, restarting wifi, etc. Nothing has worked. If anyone gets a solution, would love an update.