You will have to do the following sadly, it's a bit of work and debugging:
https://partner.steamgames.com/doc/features/leaderboards/guide

Copy paste the code and add one or more status variables which you set in the various functions and events, like findLeaderboardResult = 0/ 1/ -1. Then add a simple DLLFUNC to read their values in acknex and display them on screen for debugging. That's how I started back then.