Can not submit MSIX package

Question

For the last three to four weeks, we have been trying to submit our first ever app, which is developed from scratch, using Visual Studio 2022 and Xamarin forms.

The app is fully functional, and runs in windows, without any issues. We have followed the provided documentation (https://learn.microsoft.com/en-us/windows/uwp/publish/) and built the required MSIX package. The package has always passed the windows certification kit without any issues. After signing the MSIX package using MSIXhero, we are able to install and run the app on local machines without any problems.

But, every time when we try to submit the MSIX package, we receive the three exact following errors.

You must upload at least one package. If you are using market groups, then each market group must have at least one package.  
You must fix all package validation errors before submitting. DCwin_1.0.2.0_x64.msix18.1 MB  
Package acceptance validation error: We encountered a fatal error while parsing the package DCwin_1.0.2.0_x64.msix: An item with the same key has already been added.. Try again or upload a new package.   

After spending countless hours searching the web, we still cannot figure out why we are getting the errors shown above. First, we thought maybe it is still something wrong with the app, although the app has already successfully been published to Google Play, Amazon and App store.

Still we created a new, simple, one-page, app using Xamarin forms, and tried to upload that app's MSIX package, but to our surprise we received the exact same errors.

Meanwhile, we didn't give up and created at least 10 different MSIX packages using the suggestions that we found on the web/documentation, but always, we are getting the same three errors, which honestly, do not provide enough detail that we can follow.

Answer 1

Thank you very much for the quick reply. After following steps again, we realized that we never associated our app with the store, after re-trying we were able to submit the app and waiting for the certification now.