median_share_to_app() not working?

I added the median_share_to_app function to the very top of my site but it does not get called when sharing something from Audible or Spotify. The function in my case only holds a test alert() and does not access the actual JSON data.

I even tried the official "share to app"-app https://median.co/share/zwnmbo but there also nothing is displayed.

I tried sharing with my email app and WhatsApp and that worked as it should.

Anything that I'm missing?