No longer able to log into xfinitywifi hotspots

I've been unable to use xfinitywifi hotspots for over a week now.

After connecting to the signal, having the window pop up to enter my xfinity credentials, and then entering them, I get a page with this error message:

Access Denied

You don't have permission to access "http://login.xfinity.com/login" on this server.

Reference #18.4013817.1789582159.1e389363

https://errors.edgesuite.net/18.4013817.1789582159.1e389363

I tried and succeeded logging into my xfinity account normally using my credentials just to make sure I had them right.

I'm able to connect to other hotspots just fine.

I've tried four xfinitywifi hotspots now in different parts of the city. I get the same error every time (with different Reference numbers).

I've tried clearing cookies & cache.

I'm not using VPN or alternate DNS.

I also can't connect to the "Xfinity Mobile" signal that I've successfully used in the past, having downloaded and installed the profile.

This is on a Sequoia 15.7.9 Macbook Air. I also saw it tried once by someone from their iPhone and they ran into the same Access Denied page. My Android phone still connects to the signal fine, but I haven't had to re-login from there recently; if there's a way to force a login, let me know and I'll give it a try.