Impossible to update app package

I had an app studio app (windows 8.1) that recently was removed from the store because I failed to update the Age Ratings. Recently I requested that the app be reactivated in the store so I could submit an updated version with the Age ratings questionnaire filled out.

It was reactivated. I proceed to update my app in app studio to Windows 10. I submit the new package in Windows Dev Center, but I keep getting this error.

A previous submission for this app was released with a Windows Phone 8.1 or Windows 8.1 appxbundle. Your Windows 10 submission must also contain an appxbundle

appxbundle doesn't exist for windows 10 apps. Furthermore I don't have any previous Windows 8.1 appxbundle other than the last original that was published to the store. But in order to update I need to increment the version. Generating a new Windows 8.1 package from App Studio no longer provides appxbundle. But rather appupload files.

It impossible to update this app through dev center. What can I do?

Furthermore I don't have any previous Windows 8.1 appxbundle other than the last original that was published to the store.

Please note that once your app is published as appxbundle, it's impossible to go back to non-appxbundle format.

If you're not able to genetate appxbundle in App Studio, you can download source project and open it up using Visual Studio. Then you can follow the create an app package to generate appxbundle package for your submission.

Just select "Always" so that your app name will be _x86_x64_arm_bundle.appxupload format.