Instead of using the actual leaderboard name you have to use the Leaderboard ID. I wonder if this is the issue you are having. I had the same issue because the plugin asks for the leaderboard name and even gives an example of the name. So just create a variable with the Leaderboard ID and use that. Let me know if that's the issue you are having
Also as far as the ads quickly loading. I ran into the same issue and I narrowed it down to the event On banner loaded triggered multiple times even when calling it just once. So I used a variable in the event and changed it the very first time the On banner loaded got triggered.
I agree they should not describe it as the leaderboard name, but I've always used the ID since I started working with C2's built-in plugin, then cranberry's and both suggest using the ID. It's working now, it was a major mistake on my behalf of using the wrong package name in the game services!
Believe it or not but just two days ago I tried usign a variable that did like you described and it didn't help, I might try it again with a blank layer on the top set to active and see if that helps. At the moment, the way I have it doesn't refresh but it DOES load it again when it is unhidden, which is weird and flakey looking.