Why is the material type menu item not displayed in drupal 7?

Question

Drupal

There is a problem: the material type menu item is not displayed. I do exactly the following: I create a new type of material, then in the menu settings I select the Main menu. After that, I determine the parent element I need (This parent element is the Main Menu item, which is called Data and it is allowed to display sub-menu items). I save the material type and the newly created menu item is not displayed for the life of me. What could be the problem? How to solve it?
Thank you.

Answer 1

Maybe this comment will help: https://drupal.org/comment/4478948#comment-4478948