iCloud Authentication Errors
I've been getting authentication errors when trying to sign into iCloud from Windows 10 for quite a while. It worked before (months ago) so I've been trying to troubleshoot it the past couple weeks. Lots of Googling and some calls with Apple led me to try many things: Disable Windows firewall, uninstall Malwarebytes, disable IPV6, enable/disable NetGear router security, tried a different router from TP Link, tried connecting directly to my approved Motorola DOCSIS 3.1 modem.
The first thing that worked was connecting the laptop to the internet through a cellular hotspot with all Windows settings back to normal. In other words, not using my Spectrum home internet. Then I tried connecting my Windows laptop via Spectrum but using Nord VPN and like the cellular hotspot, it worked. So it appears that when connecting through Spectrum's servers, iCloud won't authenticate. But when connecting the same laptop other ways, it works fine.
I've sent this to Apple. I think Spectrum needs to know about it too. So here it is.