Seems like the 404 might be the issue:
From Apple's docs: When you add the meta tag to your webpage to support invocations from Safari or an SFSafariViewController, you automatically add support for invocations from links people share with others in the Messages app. When a person shares a link to the website that displays the banner or App Clip card, the recipient can tap the link to instantly launch your App Clip.
Topic:
UI Frameworks
SubTopic:
General
Tags: