jquery menu dropdown has stopped working

I am having an issue with the top menu dropdown as well as a slide menu that has stopped working. They do work only on the 404 error page but not on any other pages.

They have stopped working after I install the W3 Total Cache plugin. I enabled to js and css minify and I am guessing this must have interfered with the styles and jquery. I have uninstalled the plugin since but this has not helped to get the menus working again.

This was the element style on the dropdown menu before:

element.style {
top: 30px;
visibility: visible;
left: 0px;
display: none;
}

and when hover on it, display:none; would become “block”

But now the element style is no longer present on the menu.

Does anyone know which files I should restore or alter to get it to work again?
Any help is much appreciated.

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