This is a common mistake with Actor. You are creating an Actor, and saving it in a local variable (mNodePath). But you are not then saving that variable anywhere, so when it goes out of scope, Python cleans it up, and deletes the Actor part of the object.
The NodePath part of it remains and is visible in the scene graph, but since it is no longer an Actor it doesn’t animate.
Solution: self.mNodePath = mNodePath
David