The menu may not be displayed for 2 reasons
- The menu has a low parameter “Z-index”
- The Page has cached
The menu has a low parameter “Z-index”
Set the option “Z-index” to a higher value
The Page has cached
If you are using a caching or minification plugin try resetting the cache and reloading the page with the keyboard shortcut Ctrl+F5
Also, for testing, you can disable the caching plugin and check if the menu appears on the page