Physics Not Working on Object

I need to know why the object in this file:
will not obey gravity. I have set everything I know to in Properties Edtor => Physics and I have Rigid Body World added in Properties Edtor => Scene. Yet when it is selected its outline is yellow instead of the expected green. When a simulation is run with Alt A it does not fall.

Remove Rigid Body and then re add the rigid body
In the Object data under Groups, add it to the RigidBodyWorld group