Top navigation menu makes it easy for visitors to navigate through the Magento 2 store. Any issue with the navigation menu is not tolerable as it affects the user experience in your store!
Magento developers generally face the issue of the top navigation menu not displaying in the frontend. The product categories are not showing even after they are added to the admin panel. This is a widely faced problem in Magento development. It occurs when changes are made in the Root category. You need to look after the additional configuration settings when changes are made in the default category or new root category is created.