The second level menu on Bitrix does not work. What could be the problem?

Question

1C-Bitrix

The second level menu does not work
I have the following structure
Site root -> Folder 1 (Knowledge Base) -> Folder 2 (How osteopathy works) -> Folder 3 (Submenu)
In Folder 1 I create ".left.menu.php", add items and I display the menu template in the left sidebar (the first level menu is displayed correctly)
Next, in Folder 2 I create ".child.menu.php" I add the second level menu item (Folder 3) and it is not displayed on the site I cleared the
cache, the nesting level in the component settings is 4, the child template for the second level elements is set, nothing is hidden by styles - the elements are not displayed at all, the standard template for the menu is selected, which supports nested menu items.
I display elements simply from the root of the site, not infoblocks.
For example, https://osteopathy-plus.rf/baza-znaniy/kak-rabotae... this section should have a submenu