Error Building Win10 App on VS 2015 after updating
In your appxmanifest, set them both to 10.0.0.0. The RTM toolset injects the correct version when building.
Then in your project properties, make sure to set the target toolset version property to 10.0.10240.0 for All Configurations and All Platforms.
In your solution explorer, right click the UWP project directory and choose "Properties". Then, on the "Target Version" and "Min Version" field, click the drop down button and choose the target platform version based on your sdk, not "inherit from parent or project defaults".
This answer: https://stackoverflow.com/a/31705693/775359
This post on the forum: https://forum.ionicframework.com/t/solved-problem-running-windows-platform-on-windows-10/30216/6
In other words Windows 10 SDK is required: https://developer.microsoft.com/en-us/windows/downloads/windows-10-sdk
(also remember to update your Windows 10)