Mac App Store reviewers can't install my app

Hi everyone,

Has this every happened to you? If so, how did you resolve it?

Submitting my app for review, I got the following rejection:

Guideline 2.4.5(ii) - Performance

The package currently available in App Store Connect cannot be installed and may be corrupted.

Next Steps

Please rebuild your application and upload a new version. If this issue continues, please contact Apple Developer Technical Support for help investigating the issue.

DTS referred me back to app review:

We are unable to help you resolve this matter. Please circle back with the App Review team for assistance.

I'm building the .pkg with productbuild:

xcrun productbuild --product WFH\ Phone\ Webcam.app/Contents/Info.plist --component WFH\ Phone\ Webcam.app /Applications --sign "3rd Party Mac Developer Installer: Mansour Moufid (42A2D88R9U)" --timestamp WFH\ Phone\ Webcam.pkg

and uploading it with altool:

xcrun altool --username "..." --password "..." --validate-app --file WFH\ Phone\ Webcam.pkg --type osx
xcrun altool --username "..." --password "..." --upload-app --file WFH\ Phone\ Webcam.pkg --type osx

The .pkg signature looks fine:

xcrun pkgutil --check-signature WFH\ Phone\ Webcam.pkg 
Package "WFH Phone Webcam.pkg":
   Status: signed by a developer certificate issued by Apple (Development)
   Signed with a trusted timestamp on: 2024-04-29 14:11:27 +0000
   Certificate Chain:
    1. 3rd Party Mac Developer Installer: Mansour Moufid (42A2D88R9U)
       Expires: 2025-03-13 20:11:55 +0000
       SHA256 Fingerprint:
           CB 8A 12 1D 4D 16 29 27 08 30 07 1C 6C F6 1C F4 85 6E AE F1 B1 34 
           68 F7 81 6D C3 3B 1B 8C 5D 32
       ------------------------------------------------------------------------
    2. Apple Worldwide Developer Relations Certification Authority
       Expires: 2030-02-20 00:00:00 +0000
       SHA256 Fingerprint:
           DC F2 18 78 C7 7F 41 98 E4 B4 61 4F 03 D6 96 D8 9C 66 C6 60 08 D4 
           24 4E 1B 99 16 1A AC 91 60 1F
       ------------------------------------------------------------------------
    3. Apple Root CA
       Expires: 2035-02-09 21:40:36 +0000
       SHA256 Fingerprint:
           B0 B1 73 0E CB C7 FF 45 05 14 2C 49 F1 29 5E 6E DA 6B CA ED 7E 2C 
           68 C5 BE 91 B5 A1 10 01 F0 24

The app's signature also checks out:

codesign --strict --deep --verbose --verify WFH\ Phone\ Webcam.app 
WFH Phone Webcam.app: valid on disk
WFH Phone Webcam.app: satisfies its Designated Requirement

I have no idea what "cannot be installed and may be corrupted" means and app review is not responding to my request for more information...