The Top navigation menu makes it easy for visitors to navigate through the Magento 2 store. Magento developers generally face the issue of the top navigation menu not displaying in the front end. Here's the solution for Navigation Menu Not Showing in Magento 2!
Steps to solve the issue of Magento 2 Navigation Menu Not Showing
~ Add a root category
~ Add a subcategory of the new root category
~ Choose a new root category
Checkout video tutorials at https://youtu.be/e_4Q5nQM1b4
For more info: https://meetanshi.com/blog/solved-magento-2-navigation-menu-not-showing/