If you're developing a Windows Store app and you get the error:
...App for the Windows.Launch contract failed with error: The app didn't start
in the following Event Log:
Applications and Services Logs\Microsoft\Windows\Apps\Microsoft-Windows-TWinUI/Operational
The error may be caused because you attempted to install your app via a dism installation and then attempted to deploy it via F5 deployment in Visual Studio.
To verify this is the case you can run:
dism /online /Get-ProvisionedAppxPackages
If you see your app listed you can then remove it with:
dism /online /Remove-ProvisionedAppxPackage /PackageName:[packagename]
You don't even need to log out and log back in. Hope that helps someone somewhere.