7 – Sub-menu tree problem

I have a website built with Drupal 7 CMS and I use the submenu tree module. Everything worked well for months, but a few weeks ago, the client reported that all content links from sub-links and sub-links had disappeared. I have checked my local version of the site and there are no links either.

I've tried using the same module on another local Drupal 7 website and the result is the same – no matter how I try to configure it – it shows no content link sub-link or sub-link.

Does anyone have the same problem? Anyone using the same module – can you confirm that it works with your website?