How can I do to refresh this feature?
See: Changing fields & getting the changed data in your app. Short answer: call Activate(), IsGenuine(), or IsGenuineEx(). Any of those functions get the latest data.
There is any api function to automate this?
To automate? No. There's no way for your app on a customer's machine to know a feature value has changed.
What do you think/recomend in this case?
Add a dialog somewhere in your app that let's the user manually get the latest feature values. For example, a button that calls Activate(). Just add instructions to your purchase page (or after they purchase) that says something like "Click Help -> About and then click the 'Refresh features' button"
Does that make sense?