iCloud on Windows 15.3.138 unable to synchronise

I have this issue as well. Started last week for me, maybe the week before. I have uninstalled and reinstalled. Tested without an antivirus, on and off a VPN. My iCloud account will show the device in it lists, but nothing will sync. Had no issues before. not sure what version it started with, maybe even just when 15 was released, but currently running 15.3.138.

Windows 11 Pro 24H2 26100.2314

I am having the same issue!

Check your logs here:

C:\Users\USERNAME\AppData\Local\Packages\AppleInc.iCloud_HASHCODE\LocalCache\Local\Logs

In it, mine has the following:

CKW::iCloudAccount::RefreshBag   AOSTransactionGetError was kAOSErrorInvalidCredentials - trying to launch control panel to show auth prompt

CKW::iCloudAccount::RefreshBag    AOSTransactionGetError was kAOSErrorInvalidCredentials - trying to launch control panel to show auth prompt

CKWD::PCSIdentityManager::CopyIdentityForService  Didn't get a service identity from the PCS framework

I've scoured the internet searching for these errors, but have only found others that have posted on the Microsoft forums. Apple says contact Microsoft support. Microsoft says contact Apple iCloud support. The cycle is endless which is really unfortunate. That being said, there is no fix for this until Apple releases an updated iCloud application.

Okay.. so it's working now somehow.

Here are the steps that I performed, your mileage may vary:

1. Uninstall iCloud.
2. Restart your computer.
3. Install iTunes through the Microsoft Store.
4. Open iTunes and log in.
5. Install iCloud through the Microsoft Store.
6. Log in to iCloud (I don't believe that it asked me for a 2FA code on the first try.)
   1. Skip Photos.
   2. Allow iCloud Drive.
   3. Skip Passwords & Keychain.
   4. Skip Bookmarks.
   5. Accept Share iCloud analytics.
7. Click on "Account Details".
   1. I noted that "Your Devices" was blank and I was unable to see any devices.
   2. Click "Sign Out".
8. Sign back in (It 100% asked me for a 2FA code this time)
   1. Skip Photos.
   2. Allow iCloud Drive.
   3. Skip Passwords & Keychain.
   4. Skip Bookmarks.
   5. Accept Share iCloud analytics.
9. It started syncing for me after this!

I don't have another account or Windows computer to try on, but it works just fine on my MacBook Pro. I can sync everything normally. Wonder if something is cached somewhere on the Windows computer that is preventing the account from initialising properly on the system. Stored data that it is seeing and cannot replace/overwrite. I have deleted all mention of iCloud and Apple I can find after uninstalling the app and still no luck, even checked Windows Credential Manager to see if a store credential there but I see nothing. I can log into Apple TV and Music just fine on this Windows computer, but the iCloud for Windows just does not want to communicate. Another oddity is at the same time, I could not connect to OneDrive either, but it just started working. Performed malware scans and nothing comes up. Not sure if it is the recent update to the iCloud app or Windows.