icloud for windows not signing in

Greetings nveldman,

Security software may be the culprit for being unable to sign in to your Apple ID using iCloud for Windows.

Check out the information in the article below:

Resolve issues between iCloud for Windows or iTunes and third-party security software - Apple Support

"If your security software is causing an issue with iCloud for Windows

• You can't sign in with your Apple ID.
• You see "Verification Failed: An unknown error occurred" or "An error occurred during authentication. Please try again." 
• You see "Your setup couldn't start because your username or password is incorrect" or "Your setup couldn't be started because the iCloud server stopped responding.""

Test the connectivity to help isolate the behavior, using the steps from within the article:

"Test your connectivity

1. Check your hosts file to make sure that it's not blocking iTunes from communicating with Apple's servers.
2. If you’re having issues using AirPlay, Home Sharing, iTunes, or Remote, test the connectivity between the computers or devices in your house. They should be connected to the same network and subnet in order to function properly."

You can see additional troubleshooting steps here: If you can't connect or sign in to iCloud - Apple Support

If the issue persists, please let us know the behavior that is experienced when attempting to sign in, including any error message that is received.

Kind regards.