[Win11] Verification Failed: An unknown error occured.

Hey AlexanderLG,

We'd recommend uninstalling and reinstalling the iCloud app for Windows as that may help to resolve the issue.

This article explains how: Sign out of or uninstall iCloud for Windows

"Uninstall iCloud for Windows if you have Windows 10

1. On your Windows computer, sign out of iCloud for Windows.
2. Open Apps and Features in System Settings.
3. Locate iCloud, click uninstall, then follow the onscreen instructions.
4. If you also set up iCloud Mail in Outlook, locate iCloud Outlook, click Modify, choose Remove, then follow the onscreen instructions.

Uninstall iCloud for Windows if you have Windows 8

1. On your Windows computer, sign out of iCloud for Windows.
2. Open Control Panel, then click Uninstall a Program.
3. Click iCloud, click Uninstall, then follow the onscreen instructions.

Uninstall iCloud for Windows if you have Windows 7

1. Choose Start menu > Control Panel.
2. Click Programs, then click Program and Features.
3. Click iCloud, click Uninstall, then follow the onscreen instructions."

Thanks!