Failed to update to Windows 10 Fall Creators Update (version 1709) from ver 1703

The Microsoft stock answer is as follows.

Method 1:

You may try these steps to reset the Windows update components manually and check.

1. Press Win+X on the desktop screen of the computer.
2. Select Command Prompt (Admin)

3. On the open Command Prompt window copy and paste the commands :

   net stop wuauserv
   net stop cryptSvc
   net stop bits
   net stop msiserver
   ren C:\Windows\SoftwareDistribution SoftwareDistribution.old
   ren C:\Windows\System32\catroot2 catroot2.old
   net start wuauserv
   net start cryptSvc
   net start bits
   net start msiserver
   

4. Exit the command prompt and check.

Delete the renamed folders if everything is correct.

You can try the following step if the issue persists.

Method 2:

Check if the region is correct. Follow the steps mentioned.

1. Type "Region" on the Start screen. Click "Settings" and press Enter.
2. On the "Format" tab, select "English (United Kingdom)".
3. Click "Languages Preferences"> "Add a language" and add "your language".
4. Once added, select it and click "Move Up" to make it the first language. Close the Language window.
5. On the "Region" window, click "Additional Settings" and check if the values are same.
6. Click the "Location" tab and change the Home Location to "your country" and then click OK.

The issue is caused by some incompatible software. This was detected by windows update, after applying the Microsoft solution as mentioned by harrymc.