Plugin doesn’t work

I have the latest WordPress and I am using the Shopkeeper theme by Getbowtied.

The plugin doesn’t work for me.
– I created a new location in the DuoGeek > Menu Manager screen
– I created a different menu to put on a specific page and marked the newly created location as its location in the Appearance > Menu screen
– I went to the specific page I want the menu at, chose the main menu from the Menu Manager’s first dropdown, and the new Menu location from the second dropdown, and hit save.

When I do this then save the page, the new menu disappears from the menu manager box and the page still shows the old menu. You should check your plugin’s compatibility with the newest wordpress.