Code signing works on exe but doesn't on msix

pbertolino sorry for the delay in reverting on this question. Publishing an app on the Store should not need signing, your app will be signed with a trusted certificate for you. This allows the user to install and run your app without installing the associated app signing certificate. If you need the app signed for testing/internal publishing, you may want to try the following :
1. check if the publisher name in the manifest and the one you are trying to use to sign match
2. try using signtool.exe that comes with the SDK, to isolate the issue:
https://developer.microsoft.com/en-us/windows/downloads/sdk-archive/
3. please submit a feedback hub request with the issue detail.
4. Are you able to sign while packaging using "Create App Package" wizard?

Please update this thread with your findings. thank you.