3D WebView for Windows and macOS embeds Chromium, and Chromium is unable to run in the Mac App Store's sandboxed environment without significant modifications. So, 3D WebView doesn't currently support building for the Mac App Store, and this limitation is listed on the product page. However, I'm tracking a feature request for adding Mac App Store support, and I'll update this article when I add support for it in the future. If you want to be added to the waitlist for Mac App Store support, please contact me.
In the meantime, you can distribute apps outside the Mac App Store by notarizing them. For reference, please see this zip folder, which contains an example notarize-app.sh bash script and entitlements.plist file that can be used to successfully notarize apps that use 3D WebView. Before running this script, you must first update the values of the variables in all caps (e.g. APPLE_ID, TEAM_ID, PASSWORD, etc) to match the details for your developer account and app. After you have populated the script's variables with the correct information, you can execute it via the macOS Terminal app. If the app is notarized successfully, the script's terminal output should resemble the following:
Code signing...
./build-mac.app: replacing existing signature
./build-mac.app: signed app bundle with Mach-O universal (x86_64 arm64) [...]
Creating archive...
...
Uploading to the notarization service...
...
Successfully uploaded file
id: {submission_id}
path: /Users/example/archive.zip
Waiting for processing to complete.
Current status: Accepted...............
Processing complete
id: {submission_id}
status: Accepted
Removing archive...
Finished notarization. Next, stapling the ticket to the app...
Processing: /Users/example/build-mac.app
The staple and validate action worked!
Verifying that the app has been properly notarized...
./build-mac.app: valid on disk
./build-mac.app: satisfies its Designated Requirement
./build-mac.app: explicit requirement satisfied
Processing: /Users/example/build-mac.app
The validate action worked!
Finished verification.If notarization instead failed, you can determine why it failed by using xcrun notarytool log command to download the notarization logs.