How to cast netradio to Google Home Device

I set up my Google Home devices properly in homeassistant and already use them with the service tts.google_say.

But I fail to play netradio with the service media_player.play_media-service with these data:

entity_id: media_player.rikes_mini
media_content_id: ‘http://www.ndr.de/resources/metadaten/audio/aac/ndr2_hh.m3u
media_content_type: music

Also with
media_content_type: audio/mp3 it won’t run.

I checked it with the cast-page: https://www.home-assistant.io/integrations/cast/

But it does not work. Any idea what is wrong?

No idea what’s wrong here?

I hoped it might be easy for experienced users.