Please ensure that you created tab types in the “Product tabs” menu.
You can find more information about it here: http://webshoplogic.com/product/woocommerce-custom-tabs-pro-plugin/
(Documentation tab -> “How tab types can be defined?” section)
We suppose if you create tab types, the problem will be solved.
If so, please let me know, and we will make an error handler for notify users if there is no tab type defined.