Mostly this depends on that the C-Pen is not activated as Input Method. Check the user guide paragraph 2 how to do this.
If this is not the case it may also depend on antispyware/antivirus/anti-whatever security software.
Example: Webroot features a Keyboard security feature that - if active - prohibits C-Pen Core to input text to OSX applications. To get passed that this feature has to be paused.