Thank you for letting me know; you're absolutely right- it's not working at all now for new users, my app hasn't yet been approved to leave Spotify's development mode- https://developer.spotify.com/documentation/web-api/concepts..., so the top/tracks and top/artists endpoint which I'm using to fetch data aren't functional.

Very embarrassing on my end- wish I had more than 1 Spotify account so I could verify the API was working for new users before posting- my apologies.