can't log in icloud. Whenever I try to login, i get the below blank dialogue box. Using Windows 10

Hello jahwho,

For this issue, you'll want to first ensure there's no third-party security software that could be interfering with your ability to sign into iCloud for Windows. Resolve issues between iCloud for Windows or iTunes and third-party security software has more information on this.

"Things to check first

Before you change your security software's setup: 

• Make sure that the date, time, and time zone are set correctly on your computer. Learn how to update these settings on a Mac or on a PC. 
• Log in to an administrative user account, not a guest account. Learn how to do this on a PC. 
• Update to the latest version of iCloud for Windows or update to the latest version of iTunes.
• Make sure that you have the latest software on your Mac or on your PC.
• Make sure that you set up Windows Hello. Learn how to set it up. 
• Make sure that you only have one type of security software installed. If you have more than one type of security software installed, you might experience performance issues."

If you continue to experience issues with signing in, contact Apple Support.

Regards.