Sticky Menu not working with catch sticky menu plugin

Hello! I wanted my header menu to be sticky. I installed the Catch Sticky Menu plugin. Before I bought the theme the support said I would have to go to the desktop menu selector and change "Desktop Menu Selector" and "Mobile Menu Selector" from #primary-menu to #header-navigation-area and change Sticky Background Color as well. I did the first task but kept the background color white. However, the menu does not stick. What can I do? Thank you for your help! Nathan