IOS - action button is not visible in local push notification

Question

Following is code in objective-c to add action button during app launch -

 UNUserNotificationCenter *center = [UNUserNotificationCenter currentNotificationCenter];
 UNNotificationAction *ActionBtn1 = [UNNotificationAction actionWithIdentifier:@"Btn1" title:@"Open App" options:UNNotificationActionOptionNone];
 UNNotificationCategory *category = [UNNotificationCategory categoryWithIdentifier:@"richNotificationCategory" actions:@[ActionBtn1] intentIdentifiers:@[] options:UNNotificationCategoryOptionNone];

 NSSet *categories = [NSSet setWithObject:category];
 center setNotificationCategories:categories];

Also setting categoryIdentifier while scheduling notification -

notificationContent.categoryIdentifier = @"richNotificationCategory";

still action button is not visible. any hint please?