@DP0427 have you considered using the configuration UI? It makes setting up your remote a lot easier and I worked really hard on it 
. I wouldn’t necessarily go by the examples in the thread. The card has had four major revisions and a lot of those examples are obsoleted.
I’m assuming this is for Android TV right? This card uses the Home Assistant integrations for various media platforms to control them. Android TV supports both the media_player.play_media action with media_content_id like you’re trying, but for this card’s default sources I used remote.turn_on to launch activities. You may also want to look at the Android TV deep linking guide thread for more information on launching activities.