Any Xamarin developers here?

[MitchT]

Three of us are using Xamarin to develop an app. Currently it's running on iPhone only. In a nutshell, the app involves sharing web pages to the app and organising them within the app, like Pinterest does with photos. Anyway, for some reason two of us can no longer share things to the app. When looking at a website you tap the share button and the "share sheet" appears. Then tap the icon for the app and a pop-up should appear inviting you to save the shared item to the app. Our developer is still achieving this successfully, but the other two of us (not developers) can't anymore. If we tap the app icon in the share sheet, nothing happens. The app was deployed to our phones via App Center in case that's relevant. Our developer has suggested signing up for an Apple Developer account and deploying the app via Testflight instead, but if the problem is in this app the problem might simply be duplicated, not eradicated. Any ideas?