It appears to be a bug in the latest version of Microsoft.NETCore.UniversalWindowsPlatform. Rolling back from 6.2.2 to 6.1.9 fixes the issue.
Success at last !! Thanks to Tim.
I manually downloaded and installed the UWP 6.1.9. VS2017 does not install this via the Nuget Pakg Manager.
Built the packages and uploaded. The submission has finally gone through.
This submission failed with error code(s) 1201,1201 . More info about the error(s) can be found here.
Were you able to solve this? I'm running into the same issue.
Submissions have been working great until updating Microsoft.NETCore.UniversalWindowsPlatform and Visual Studio (not sure which is the culprit but suspect the former).