Using an older version of Windows 10 can cause issues downloading the Sling TV app from the Windows Store. To resolve this issue, Microsoft recommends that you install all OS updates.
To check for updates, start at the menu represented by the Windows icon. Click on Settings. Scroll all the way down the Settings menu and find Update & security. Click on Windows Update. Click on Check for updates. Your device should update to the latest version of Windows. If your problem persists, please check your network connectivity.