Classic issue with Universal Links, assuming you're on iOS. I implemented Universal Links for an app a few years ago. I think many developers think it's trivial to implement, follow the one-page guide to setting it up, and think the feature is complete. In reality it's much more complex to do for an app of any real size.

They probably need a wildcard in their routing to open a webview for stuff like this they can’t handle in the app. But yes universal links are tough to get right. Easy initial implementation and then surprise bugs forevermore :)