Migrated site to v1.5.4 and having a small issue with categories

[drgr33n]

Still can't get to the bottom of this. Trying to work my way through the code but can't figure it out. When I create a category I get the correct information in the database. Categories & Categories_description are populated with the correct information and nothing is different to anything else. Then I allocate a couple of products and the product exists in the database with no information missing but still if I allocate the product to a new created category the products are not shown.

What makes me think maybe a template issue or something ?. Does anyone know where to look for code relating to how the product list is being generated ? I've used the developers tools included to search and found this but I can't see how it wouldn't function.

// Construct a category path to the product
// TABLES: products_to_categories
  function zen_get_product_path($products_id) {
    global $db;
    $cPath = '';

    $category_query = "select p.products_id, p.master_categories_id
                       from " . TABLE_PRODUCTS . " p
                       where p.products_id = '" . (int)$products_id . "' limit 1";


    $category = $db->Execute($category_query);

    if ($category->RecordCount() > 0) {

      $categories = array();
      zen_get_parent_categories($categories, $category->fields['master_categories_id']);

      $categories = array_reverse($categories);

      $cPath = implode('_', $categories);

      if (zen_not_null($cPath)) $cPath .= '_';
      $cPath .= $category->fields['master_categories_id'];
    }

    return $cPath;
  }

////

If I search using DTK through the template files I see loads of references so was just wondering if someone knows what files responsible for generating the list of products ? Zen cart is huge nowa days