Need help understanding error "manifest is not in the package root" while registering Windows 10 package

I am trying to register the Windows 10 Edge package with Windows Server 2016. I have successfully installed the store thanks to a forum I found and it opens but remains untested. I am trying to do the same with Edge. I've copied the app package from the installer iso to C:\Windows\systemapps and ran the power shell script:

Add-AppxPackage -register "C:\windows\systemapps\Microsoft.MicrosoftEdge_8wekyb3d8bbwe\Appxmanifest.xml" -DisableDevelopmentMode

And get the following error:

Add-AppxPackage : Deployment failed with HRESULT: 0x80073CF9, Install failed. Please contact your software vendor.
(Exception from HRESULT: 0x80073CF9)
Rejecting a request to register from Appxmanifest.xml because the manifest is not in the package root.
NOTE: For additional information, look for [ActivityId] a80e1223-2787-0000-dc3e-12a98727d301 in the Event Log or use
the command line Get-AppxLog -ActivityID a80e1223-2787-0000-dc3e-12a98727d301
At line:1 char:1
+ Add-AppxPackage -register "C:\windows\systemapps\Microsoft.MicrosoftE ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo          : WriteError: (C:\windows\syst...ppxmanifest.xml:String) [Add-AppxPackage], IOException
+ FullyQualifiedErrorId : DeploymentError,Microsoft.Windows.Appx.PackageManager.Commands.AddAppxPackageCommand

I've verified the manifest is in the package root so other than that I can't figure out what it means. Can someone help me understand what it's looking for?

Reference for store install: http://virtualcustoms.net/showthread.php/72904-Install-Microsoft-Store-and-Apps-on-Windows-10-LTSB-2016

I was just trying to do the same thing and I have found if I copy the app to C:\Program Files\WindowsApps then it installs without complaining about not being in the root and then the Edge icon also appears on the start menu.

The command to run is:

Add-AppxPackage -DisableDevelopmentMode -Register "C:\Program Files\WindowsApps\Microsoft.MicrosoftEdge_8wekyb3d8bbwe\AppxManifest.xml"

Whilst this allows the app to install and I am able to launch it from the start menu it closes after about 2 seconds and looking in the log (Application and Service Logs\Microsoft\Windows\Apps\Microsoft-Windows-TWinUI/Operational it shows this error so it looks like there is still something else that needs to be done to get this working:

ActivateApplicationForContractByAppIdAsUserWithHost of the app Microsoft.MicrosoftEdge_8wekyb3d8bbwe!MicrosoftEdge for the Windows.Launch contract failed with The app didn't start..

Robin