Enabling plugin removes my dropdown menu and changes link behavior

First, this plugin is excellent. Second, I have NO programming experience, so please bear with me.

I need to display an image in my menu which links to an external link. This does that beautifully, but:

enabling the plugin automatically makes all sub-menu items disappear. The icon to drop down the submenu disappears altogether.

In addition, my site is a one page site with multiple links that take you to different parts of the homepage. Enabling this plugin makes my links behave as a multipage site instead of a one page.

Any help you can offer is greatly appreciated because this is nearly perfect.

Thanks.

https://wordpress.org/plugins/menu-image/