iCloud encountered an error while trying to connect to the server

No browser worked. I removed IPv6 and it worked then, fine. Having seen your post I reenabled it and disabled the Intel Killer prioritisation, which worked perfectly (genius!). However, three hours later, it reenabled itself, so had to go back and redo it. Hope they fix this soon.

Disabling IPv6 (128 bit) protocol resolves the issue. Yes. However, that is a terrible solution. Why am I forced to disable a newer protocol? I would understand if I would have to disable IPv4 (32 bit) because Apple is a modern company that is moving away from legacy protocols. This ridiculous. Anyone from Apple monitoring this? This is a bug and it needs a fix on Apple side!

This was happening to me. I couldn't login to icloud.com or through the app on my PC. I was able to fix it by switching off Starlink. I have a back up internet (remote worker from home) and switching from Starlink to another provider cleared it up both on the web and the app. Do the folks that have this issue use Starlink?

I use Chrome and keep getting this error. I tried Edge, still the same error. Then I tried Firefox and was able to get in. Thank you to whoever mentioned this in the thread!

This was definitely related to the Killer Intelligence app for me.

Disable/delete before you try anything else!!!

Same issue, but was able to get iCloud.com working on Firefox. Still receive "An error has occurred during authentication" error when trying to launch app on Win 10.

Opera One (v 101.0.4843.43) - FAIL

MS Edge - FAIL

Goggle Chrome (v 116.0.5845.140) FAIL

Firefox (v 117.0) WORKS (for now)

The same thing was happening to me. I contacted support and they said to reboot my pc. I tried that, and still got the same message. Don't bother clicking any of the "help" links on other pages like this one - they take you take ads for iCloud.

I MANAGED TO GET PAST THE ERROR: I just kept hitting the OK button really fast until it finally let me through. I know it seems crazy (I was feeling so when I tried it), but it actually works (at least for me). It only took about 5-8 seconds of clicks, don't keep trying for too long. It shows that there is something wrong with the service that should be looked at and addressed.

The problem of not being able to logon to iCloud.com is caused by the "Killer Network Service" Read this for details > https://helpdeskgeek.com/windows-11/what-is-the-killer-network-service-in-windows-and-is-it-safe/

Removing iPV6 worked! Everything - web, Oulook and the PC App are working as expected.

Removing iPV6 worked! Everything - web, Oulook and the PC App are working as expected.

Many Thanks!!!!

Firefox didn't work but taking off IPV6 did. Still having issues in Sept

The deactivation of the Killer Priorization Engine was the solution for me! No need to change any network settings. Thanks @borris14

Also, oddly enough, using a private browser works.

Yes, a hassle with Chrome, but Firefox works well. Go figure!