Error 500 on registration

[Baafs Academy]

Hi, 

I keep getting error 500 when I try to register  for a course I created. here is a copy of the error log, please help if you can. thanks

1. 2015-10-25 01:47:02.320

   Error dispatching POST to /first/register: 
   Traceback (most recent call last):
     File "/base/data/home/apps/s~baafsacademy-1108/1.388082362709051074/controllers/sites.py", line 1401, in _dispatch
       handler.dispatch()
     File "/base/data/home/runtimes/python27/python27_lib/versions/third_party/webapp2-2.5.2/webapp2.py", line 572, in dispatch
       return self.handle_exception(e, self.app.debug)
     File "/base/data/home/runtimes/python27/python27_lib/versions/third_party/webapp2-2.5.2/webapp2.py", line 570, in dispatch
       return method(*args, **kwargs)
     File "/base/data/home/apps/s~baafsacademy-1108/1.388082362709051074/controllers/utils.py", line 1200, in post
       labels=self.request.get('labels'))
     File "/base/data/home/apps/s~baafsacademy-1108/1.388082362709051074/models/models.py", line 1473, in add_new_student_for_current_user
       nick_name, additional_fields, handler, labels)
     File "/base/data/home/apps/s~baafsacademy-1108/1.388082362709051074/models/models.py", line 1010, in add_new_student_for_current_user
       user.user_id(), user.email(), nick_name, additional_fields, labels)
     File "/base/data/home/apps/s~baafsacademy-1108/1.388082362709051074/models/models.py", line 1026, in _add_new_student_for_current_user
       key_name, user_id, email, nick_name, additional_fields, labels)
     File "/base/data/home/runtimes/python27/python27_lib/versions/1/google/appengine/api/datastore.py", line 2732, in inner_wrapper
       return RunInTransactionOptions(options, func, *args, **kwds)
     File "/base/data/home/runtimes/python27/python27_lib/versions/1/google/appengine/api/datastore.py", line 2630, in RunInTransactionOptions
       ok, result = _DoOneTry(function, args, kwargs)
     File "/base/data/home/runtimes/python27/python27_lib/versions/1/google/appengine/api/datastore.py", line 2650, in _DoOneTry
       result = function(*args, **kwargs)
     File "/base/data/home/apps/s~baafsacademy-1108/1.388082362709051074/models/models.py", line 1062, in _add_new_student_for_current_user_in_txn
       StudentLifecycleObserver.EVENT_ADD, user_id)
     File "/base/data/home/apps/s~baafsacademy-1108/1.388082362709051074/models/models.py", line 719, in enqueue
       transactional=True)
     File "/base/data/home/apps/s~baafsacademy-1108/1.388082362709051074/models/models.py", line 738, in _internal_enqueue
       task.add(cls.QUEUE_NAME, transactional=transactional)
     File "/base/data/home/runtimes/python27/python27_lib/versions/1/google/appengine/api/taskqueue/taskqueue.py", line 1134, in add
       return self.add_async(queue_name, transactional).get_result()
     File "/base/data/home/runtimes/python27/python27_lib/versions/1/google/appengine/api/apiproxy_stub_map.py", line 613, in get_result
       return self.__get_result_hook(self)
     File "/base/data/home/runtimes/python27/python27_lib/versions/1/google/appengine/api/taskqueue/taskqueue.py", line 1950, in ResultHook
       raise _TranslateError(e.application_error, e.error_detail)
   UnknownQueueError

2. E2015-10-25 01:47:02.321

   Server error accessing the course /first. HTTP status code: 500.