Ok I checked your site .I found that you are not using traditional variable product for your course.
You are actually using woocommerce subscriptions for your course for which api support has not been added yet .
That is why the api is not able to fetch any information about pricing coz subscriptions are slightly different structure .
We will be integrating the woocommerce subscriptions in app soon .
We could integrate the buying process easily but implementing subscriptons will take some time.