I have seen this issue, it was mentioned by @xython in: Leaderboards empty - CoCo Library of Alexandria burnt?.
Is this what you mean?
Yes this is that I mean.
They don’t show up for me either on any levels, not just the free ones
Wait a little longer, up to a minute or so 
as for free levels of Kithgard Dungeon almost impossible
but since ~70% of Backwoods forest if you try several times and wait up to 60s, it can load
Sarven Desert and so on almost guaranteed load if i wait up to 60s
premium levels
since the first level of Backwoods forest if I wait up to 60s
it loads most of the time