Failed to verify your identity. Try again.

something started happening today that hasn't happened before.

summary: when I try to log into apple ID or developer.apple.com, anywhere on my LAN, wired or wireless, with all firewall and security turned off, it says "Failed to verify your identity. Try again". If I say "forgot password", I am able to go through the change my password steps. It will notify my phone with 2 step verification. When I am done with everything, and try to log in, I get the SAME ERROR. This only started happening when I started messing around with profiles & certificates on apple's developer site AND messing around with adding and removing accounts from XCode and VS 2019 for the Mac. But once Apple started throwing up the Failed to Verify error, I couldn't log in from any machine on my LAN: MacBook #1, MacBook #2, Windows PC, Mozilla Browser, Safari, Edge, you name it, I couldn't log in. It was as if Apple had blocked my IP address range.

So, I tried in front of my firewall router. I set up a laptop between my ISP gateway and my internal LAN router. Still couldn't log in.

So, i tried my work's computer, on a VPN. This WORKED.

I tried my phone, only hooked up to cellular. This WORKED.

I tried my phone, hooked up to wifi. This FAILED.

Again: Anywhere at my house, downstream of my ISP gateway, fails. This worked yesterday, before I started monkeying around with downloading certs and provisioning profiles from Apple.

Weird. And i am totally disabled here at my house for doing development.

I am not about to call my ISP and ask them, "are you disabling Apple's development protocols, any certain ports or IP addresses? Is Apple doing some kind of weird querying where you interpret it as a DOS attack?" The 16 year old that answers the phone for tech support at Frontier Internet would scratch his scruffy chin fuzz and say, "Nope. We sure don't do that. Thanks for calling. You're a valued customer! Good bye!"

PS:

Eric Root need not reply to this. His answers on the internet forums thus far (reboot your browser. Reboot your machine. Try resetting your OS. Try entering ABC123.) are INFURIATING and useless.

I'm pretty savvy about how this password stuff works. I've been a dev at Microsoft for 23 years now, and I know how this stuff generally works. Resetting my browser or clearing its cache isn't going to help. I've tried this on 5 machines, on several browsers. I disabled all of my router's firewall and security features and scanned its refusal log. Nothing. I do believe that something on Apple's side thinks my IP address is to blame, so it won't authenticate anything from this location. Can anybody genuinely confirm or deny?