Links (hrefs) not working on Android

My hrefs, specifically the TEL and MAILTO, do not work properly on an Android device. I currently have deployed two apps using Median and they both have issues with this:

I get a popup that says "App is not installed." on one app.
The app crashes on the other

I have checked the documentation and it doesn't really give much information. Is there something special I need to do? Here is the exact line in HTML (number obviously omitted)

Please note, my link-handling rule for "Non-web links", is set to external. In addition, while using the web version this functionality works fine.

Please inform me of what I can do to fix this issue.