Hi there. I moderate for a small game called Night of the Full Moon (speedrun.com/nofm). I was recently made aware that for all the categories other than the main Any%, no runs are showing on the leaderboard. 

I've accepted runs through, and they're showing up on peoples individual runs list (i.e. speedrun.com/user/Waking_Nylou).

I've got the same setting for each category, so I'm not sure what's going wrong here. Any advice would be appreciated

Its tough to say if we can't see the board settings. Could be variables, could be something else.

That is most probably because the "Class" variable has a default value. Default values for variables are values which are automatically selected when someone submits a run, and also the leaderboards are filtered by it by default.
Set the variable to not have any default value, and it should be fixed.