To be able to help you troubleshoot this, we would need to see your blocks or have a link to your project.
A Google Search for leaderboards Thunkable turns up this topic with a post be… me: Displaying and Sorting a Leaderboard - #6 by tatiang
That would be if you want to use lists. I would use a local data source myself. That way you can use multiple columns for username, score, etc.