Magento

At my website, I have created categories as I desired, and sample products below.

I am using the modern theme. However, there is no code under <ul id="nav"> </ul>
which means that there is no menu.

How do I display the navigation drop-down menu so I can display the categories on the website? Have I done something wrong in setting up the categories?

Thanks

You haven’t done anything wrong.  You need to go into your store configuration and set the default category to show then they should start showing up.  This confused the hell out of me too

Ok. I have set the default category as the Root Category, now I have a 500 Internal Server Error?

Thanks.