I’ve had similar issues on an LG smart TV and a thread here dating back to November. Still no replies there except from people having same issues. Eventually I gave up on it and disabled the skill. Someone mentioned that these issues have been around for a few years so I’m not holding my breath but would be nice to have it working. I was also experiencing problems when trying to stream to my windows player, it just showed some general error and pointed me towards the forums for help.
My Alexa, recognize the player ok, and when I ask to play a particular think, she says enjoy watching…but nothing begins in my Samsung smatTV Plex player,
It works ok with other players such as IPhone , iPad or Apple TV