Let's say you queue a link like https://www.youtube.com/watch?v=lcg6wekmCRA&list=PL6vAHxySmK2ifoStvlRGKN6RiYsB-kF8g&index=2&t=0s
But Groovy only plays one song.
So, what went wrong here?
The reason is simple: The link you queued isn't a link to a playlist, but a link to a song in a playlist.
And because people often queue links without knowing they are in a playlist, Groovy only plays that song instead of the whole playlist.
Now how do I fix this?
There's two solutions.
Solution 1: playing a direct link to a playlist
You can get this link by clicking the title of the playlist on YouTube.
You'll land on a page like https://www.youtube.com/playlist?list=PL6vAHxySmK2ifoStvlRGKN6RiYsB-kF8g
If you now play that link, it'll queue all the songs in the playlist.
Solution 2: use the -a flag
If this doesn't work, you can try using the -a flag. For more help, see Advanced Usage: Flags.
Your resulting command would look like
This will too play all songs in the playlist.