The free version was working, updated to pro. Followed all instructions and pro navigation not displaying on website.
Could you provide more info so we can investigate further. URL for the website would be a good start.
Moreover, Have you double checked that you have selected groups of users to show the menu. Please go to the “display” tab in the plugin control panel and check the roles that are allowed to see the menu. When upgrading to pro version this is the most typical issue other users are finding too.