Microsoft Store is unable to validate the .msixupload file packaged by Visual Studio. The solution file consists of a WPF app, a UWP app for XAML Island, and the MSIX Packaging Project.
The error returned at the Partner Center site is:
Package acceptance validation error: You cannot submit pre-compiled .NET Native packages. Please upload the Microsoft Store appxupload file and try again.
The .msix generated along with the .msixupload can be installed and run locally with no issues. It also passes the Windows App Cert Kit tests.
What is the potential cause of this validation error? Searched high and low for it.
You need to add reference to UWP project in MSIX Packaging Project.