Q: iCloud for Windows authentication problem

I feel your pain. W10 is its own animal. See if you can find a similar work-around for this - maybe booting in safe mode (does that even exist anymore) w/ networking or something. I am REALLY confident it's not the end user, it's Apple's end.

Well, here is another update, for what it's worth. I had more problems w/ it, so I uninstalled both icould and itunes, then rebooted my machine. Again, I'm on W7-64 bit. I then reinstalled icloud, but I chose "as an administrator". Then I reinstalled itunes. Rebooted again, and for some strange reason it now seems to be stable, and no more authentication error. We shall see.

Update: I applied the recent (July) iCloud for Windows update and the latest iTunes update, but the authentication error still persists. Again, I'm running Windows 10 64 Professional.

Sorry I could not help.  Have the same problem installing on a new Win 10 Dell computer. Have tried everything others have already suggested. Hope someone can figure it out.  Have all my contacts on the cloud and cannot access them on my PC without having to retype everyone back in. Why MS and Apple cannot resolve their issues after ALL these years is beyond me.  Frustrating.

I am not sure if this is a workaround, but see if this works at least for your contacts. I just thought of it. If you have all of your contacts in your iCloud, that means you should be able to access them on icloud.com. If you click on the little gear in the lower left hand corner (I'm trying to attach a screenshot), you have the option to export as vCard. iCloud lets you select all, so you should be able to export all of your contacts that way. You can then import that into Google contacts, Outlook or whatever you choose. Let me know if that works for you. The desktop app is just really a syncing mechanism between your desktop and your cloud, but you can import stuff into the cloud directly from your computer, much like w/ Dropbox. Keep me posted.

PS. If you have a Google account and you add that to your iphone, you should be able to sync your calendar, contacts etc. w/o a hitch. https://support.google.com/mail/answer/2753077?co=GENIE.Platform%3DiOS&hl=en

Thank you for your help.  It was a little more complicated but easily doable once the files were converted to vCard, exactly as you suggested, with the help of the following link: https://support.office.com/en-us/article/Import-contacts-to-Outlook-bb796340-b58 a-46c1-90c7-b549b8f3c5f8 . I was able to get ALL my contacts moved.  I could not have do it without your help.  Thanks again. Hopefully others will see your response.

You bet. I am glad this worked and that I could be of help in some small way. It is so frustrating when you hit a roadblock like this.

Two months ago, I contacted Apple Support (in Ireland) for this issue.

I spent almost half a day on the phone with them , provided very detailed logs to resolve the issue.

Two months later:  I have received no response from them ?! (no mail, no phone call, Nothing!!)

Forget about using Apple support for business, it is not a real support for customers.

As an IT professional, I can not afford to work with products or services from a company with no real customer support  (professional or not).

I'm now working without any Apple products or services without any problems.

Good luck!

I had same problem yesterday after install it with my Windows 10, tried many times all with same error prompt. Today before I am going to uninstall it, I think let me try last one - it works. Nothing was changed since yesterday, but it works now. Just FYI - maybe iCloud needs some time (I sync iCloud yesterday)

After nearly three weeks of nearly tearing my hair out, I finally FIXED THE **** THING!!!!!!  YAY!!!!!!!!!!!!!!

The secret was to uninstall the CURRENT  icloud for windows and find an archived version  of an earlier version of icloud for windows (google it) and install it.  The earlier version (I used 3.1 ) works fine!!