I also faced the issue and found the reason and fixed...
So anyone facing this issue can try the below unless there is any step missing and the utility is throwing validation..
- Search turn windows feature on or off
- Click on the plus sign against .NET framework 3.5 (includes .NET 2.0 and 3.0)
- Select the new option and that option as well
- click on okay.... restart the excel based utility and then try generating the json again.