App2app are made possible by policies governed by iOS and Android.
The app2app articles in our knowledge base are a culmination of our experiences to date with app2app, but they are not extensive. For more detailed resources, we advise you to consult other app2app resources (e.g. iOS and Android policies).
Our client care team does not provide support for any app2app implementation issues.
Check if there is a mistake in your Universal Links implementation. Use Apple's App Search API Validation Tool to verify your application follows the best practices.
Here's an example of what it should look like when the implementation is correct:
And here's another one where the Universal Links implementation was not correctly implemented:
What to do next?
Check this troubleshooting guide from Apple to identify the root cause.