A number of people who are using Windows Update to download and install the Windows 10 Fall Creators Update are experiencing problems. Windows 10 has a troubleshooter that can help identify any problems.
This can also reset the Windows Update app, which can help kickstart the installation.
To do this, click the Start menu, then click the cog icon on the left, which will open up the Settings window. Click on ˜Update & Security" then ˜Troubleshooter". Click on ˜Windows Update" then on ˜Run the troubleshooter" and follow the instructions, and click on Apply this fix" if the troubleshooter finds a solution.