I got this error while i tried to print a collection from MongoDB Realm database

INVALID_SESSION(realm::app::ServiceError:2): invalid session: access token expired

Here is my code :

Realm.init(this);

        app = new App(new AppConfiguration.Builder(Appid).build());

        Credentials credentials = Credentials.emailPassword("XXXXX@gmail.com","XXXXX");
        app.loginAsync(Credentials.anonymous(), new App.Callback<User>() {
            @Override
            public void onResult(App.Result<User> result) {
                if(result.isSuccess())
                {
                    Log.v("User","Logged In Successfully");

                }
                else
                {
                    Log.v("User","Failed to Login");
                }
            }
        });

User user = app.currentUser();
                    mongoClient = user.getMongoClient("mongodb-atlas");
                    mongoDatabase = mongoClient.getDatabase("doctordata");
                    MongoCollection<Document> mongoCollection = mongoDatabase.getCollection("data");
                    Document queryFilter = new Document().append("userid",user.getId());
                    RealmResultTask<MongoCursor<Document>> doc = mongoCollection.find(queryFilter).iterator();
                    final String[] da= new String[1];
                    doc.getAsync(task->{
                        if(task.isSuccess()){
                            MongoCursor<Document> results = task.get();
                            while (results.hasNext()){

                                Log.v("User",results.next().toJson());
                            }
                        }else{
                            Log.v("User",task.getError().toString());
                        }

                    });
                }catch(Exception e){
                    e.printStackTrace();
                }
 ```