Hi,
if you happen at least once to receive this unpleasant message:

“Unable to activate Windows Store app: The App.exe process started, but the activation request failed with error ‘The app didn’t start.”

that not allows you to start the Store App, here the possible causes:

1) Download assemblies via Nuget
Nuget in the Windows Store Apps will try to add an app.config in the project, but Windows Store Apps don’t need App.Config.

Solution
Remove App.Config and Deploy App.

2) Change the Package Name in the manifest

Solution
Uninstall App from the Start Screen, delete bin/obj folder and files and then Deploy App.

3) In All other cases

Solution
Uninstall App from the Start Screen, delete bin/obj folder and files and then Deploy App.

Enjoy
Maurizio