Data_template should be data, and the line in question needs double quotes around the value of the entity_id key (before the M of media player and after the last } ).
I tested it again and the code containing a call from media_player.play_media was right, the problem was simply an earlier call in another script that was not connected to a tv.
Thanks for the help.
Thanks for the help.
I tested it again and the code containing a call from media_player.play_media was right, the problem was simply an earlier call in another script that was not connected to a tv.