Theres something strange about your testing, as I said the only situation the boolean returns false is in the case of a exception (ie. the google javascript is not loaded), otherwise its true, even if the checkbox is not ticket. So a captcha that is not loaded (success=false) should return different result from one that is loaded but not ticked (success=true, token=empty).
Anyways, check the Render event to see if the captcha is loaded:
If you can attach your module I'll take a look at it.