looks like the songs aren't playing because you added a full playlist link rather than just the video id, which the little bit directly after the "watch?v=" and before the "&list= in playlists", or it's a little easier to see if you click on the share link at the bottom of the video and look the link it gives you there, it'll be the numbers and letters after the https://youtu.be/ bit! then you can replace where the code says "VIDEOID" with that!

and then the next button not showing up is just because of the length of the first song title, which you can adjust by changing the number where it says "font-size: 100%" right before the name input (anything under 86% should work in this case)! tbh that being unclear was on me, i'll update the base code to make the height work a little differently so the next button will overflow instead of being hidden, thank you for helping me realize that oversight!

here's the working code ! https://pastebin.com/QcpKSJZE