Sub-menu in the reactive drop-down menu does not open

Hello
Thank you very much in advance to all who can offer their help.

I have a basic responsive horizontal navigation menu on re-rebel dot com. They work great on a standard-sized browser, but when I look at Android, or the PC browser is reduced to the same size, the drop-down menus do not work anymore. The menu narrows nicely to a button (and opens when we click on it), but not the others.

The style sheet and the java files are in the folder www.re-rebel.com/css (a separate css file is found there for the menu, which should make navigation easier). In addition, the css for the rest of the website is in the style.css file, a higher level, in the root directory (ie www.re-rebel.com/style.css).
SEMrush

This menu comes from cssmenumaker.com if that helps you.

Thanks again!