Anyone know the "trick" to generate a .appxupload package for HoloLens?

I seem to have one build that worked and uploaded to the Windows Store, and it ends in .appxupload.

The problem is, I cannot seem to recreate the build. Everything I generate is a .appx or .appxbundle file which will not upload to the Windows Store.

I get this error even though I am building under the Store menu option:
"Package acceptance validation error: This package wasn't built for submission to the Store. Make sure you're uploading a Release build with the .NET Native tool chain enabled. http://go.microsoft.com/fwlink/?LinkId=797528"

Does anyone know the exact settings I should be using?

I am using the following:

1. VS: Release
2. VS: x86
3. Unity: Unity C# Projects
4. Unity: D3D
5. Unity: .Net with .Net Subset

Code does deploy to the HoloLens without issue.

I am running Unity 2017.1.0f3 with VS Pro 2017.15.0 and trying to upload a HoloLens package.

 

Looks like I may have found it via another forum!!

"[SOLVED] right-click your project then choose properties, go to Build and tick "Compile with .NET Native tool chain". Noob mistake ^^"