You have no ODE body here in your code, only an ODE geom. A geom by itself can only be used as a static object such as terrain.
You must assign it to a body with geom.setBody if you want it to simulate. Mass is set on the body with body.setMass, not on the geom.
Be careful though if using trimesh as a simulated object, it is very slow compared to the other geom types.