I’ve seen this topic reporting a similar problem. This one is solved, and the last release of Cesium for Unity (1.0.0) solved the error. My problem is similar: after adding a DynamicCamera to my project in Unity, I’ve a ArgumentException (see picture below), but for the Y axis.
As in the mentioned topic, the proposed solution does work: duplicating the Vertical input, renaming it YAxis and binding it as a Joystick Axis (as type) solve this error.