Access denied for IPad calender in some devices and working fine in some devices

Question

I am facing strange problem, in few IPAD i am not getting prompt to access calender but in few IPAD same code is working fine and promot is displaying to access calender.

Please let me know where i am wrong. I am using Xocde 4.6.3 and running on IPAD with IOS 7.1.1

I am new to objective C, i created one hybrid app and added below code access Calender from my app.

 - (void)viewWillAppear:(BOOL)animated
 {
     // OCT15 - Demo
    [super viewWillAppear:animated];
    [self.navigationController setNavigationBarHidden:YES animated:YES];
    self.eventStore = [[EKEventStore alloc] init];
    self.eventsList = [[NSMutableArray alloc] init];

    if ([eventStore respondsToSelector:@selector(requestAccessToEntityType:completion:)])
    {
        [eventStore requestAccessToEntityType:EKEntityTypeEvent completion:^(BOOL granted, NSError *error)
        {
            calendarFlag = @"TRUE";//April16

            if (granted)
            {
                self.defaultCalendar = [self.eventStore defaultCalendarForNewEvents];
                [eventsList addObjectsFromArray:[self fetchEventsForToday:NULL]];
            }
            else
            {

            }
        }];
    }
    else
    {
        self.defaultCalendar = [self.eventStore defaultCalendarForNewEvents];
        [eventsList addObjectsFromArray:[self fetchEventsForToday:NULL]];
    }

    if (editEventFlag == TRUE)
    {
        [eventsList addObjectsFromArray:[self fetchEventsForToday:NULL]];

        [self eventsdisplay];
    }
}

I found out few things, if my ipad is having more than 1 calender in Settings > Mail, Contacts, Calendars. and make them has default everything works fine. But again if i choose calender(ios one) app won't work.

How to fix this issue?