Hey there. I am the AVmusic skill developer. This problem, as you have noticed, has been an issue for the Pi for quite a while. Unfortunately, there is not much that I can do about this due to the internal Mycroft changes. Here is the link to the discussion in the chat about this - https://chat.mycroft.ai/community/pl/1niy3c98s7ynueuy4x9s4sixxw
And here is the link to the reported issue in the skill itself - https://github.com/reginaneon/AVmusic/issues/2
Steve says that the fix should come from their side in about 1,5 weeks time. Before that happens it appears to be a desktop-only skill. Feel free to contact me directly in the chat as well, my username is the same as it is here.