Mechanical Turk HITStatus is always unassignable

I am using the Python library Boto3 to create ExternalQuestion hits. The hit is created successfully, but the HITStatus always says unassignable. I think sometimes I receive a submitted hit, but I am not sure. Is this a bug in the library or is there a bigger issue that I am overlooking? From the docs.. "When a HIT is created, its HITStatus initially has a value of Assignable, which indicates that it's possible for a worker to accept it and begin working on it." Thanks in advance.