I just went from version 3.something all the way up to 6.2.1. Deleted 3.something and installed 6.2.1 and for the life of me I cannot get our menu to appear at the top of the page. I had it at one point, but I don’t know what I did to get rid of it. If I go into Customize Menus, Main has an option selected.
Contact with your purchase item author hope they will help you out from your issue.
go to Appearance => Menus and set the primary menu as your header top menu. Hope this will fix the menu issues. Otherwise you can check theme documentation or contact author.