Toggle closed captioning on and off during a presentation

I am working on a project where the client wants the project to start with closed captioning off, but allow the user to turn it on and off again if they wish.

I thought this would be simple...but it appears that it isn't.

If I use the toggle to turn closed captioning off at publish from the Project Properties, the CC button in the playbar remains grayed out and clicking on it doesn't reveal the captions if the user wants them on. The same is true if I publish with captions on but use an On Enter action on the first slide to turn captions off via setting the Project.ClosedCaptions variable to False.

If I publish with captions off and then use a button to allow the user to turn captions on via setting the Project.ClosedCaptions variable to True, this does activate the captions- but then the playbar CC button does not work to turn the captions off again. 

Is there any way to publish with captions off as the default, but allow the user to turn them on and off again at will?