Google Play leaderboard won't show - "Hmm, something went wrong in play games"

Hi,

So the user can login fine on the device but when pressing the leaderboard button I get a Google error (on the device) "Hmm, something went wrong in play games".

I've intergrated GPGS stuff without issue several times in the past and have also tried deleting and re-adding a new leaderboard to no avail. Here is my code :

 public void OnShowLeaderboard()
     {
         LeaderboardManager.ShowLeaderboard();
     }

Any help greatly appreciated.