Did Social.LoadUsers() stop working?

Social.LoadUsers() used to work for me, but now the callback doesn't even get called. It used to work for me previously but now nothing happens. I'm using Unity3d 5.3.1 and Xcode 7.2. I know the function gets called, the local user is logged into GameCenter and the userID array contains userIDs.

The relevant code:

 if (userIDs == null || userIDs.Length != scores.Length) {
     userIDs = new string[scores.Length];
 }

 for (int i = 0; i < scores.Length; i++) {
     userIDs[i] = scores[i].userID;
 }

 Debug.Log ("request user names");
 Debug.Log (Social.localUser.authenticated);

 Social.LoadUsers(userIDs, users => {
     Debug.Log(users.Length);
     Debug.Log(scores.Length);

     for (var i = 0; i < users.Length; i++) {
         Debug.Log(users[i].userName);
     }

     if (users.Length == scores.Length) {

         Debug.Log("!! sending scores out " + scores.Length.ToString());

         if (request.function != null) {
             request.function (scores, users, request.chunk, request.from);
         }
     }
 });

Running this outputs the following into the Xcode console:

1. userIds ("G:" and some numbers)

2. "request user names"

3. "True"