Magento product category show only default category Because the problem is that wrong children count in Table. set the children count of all children to 1.
Please take a table back up before use this script.
UPDATE catalog_category_entity SET children_count = "1" WHERE children_count < 1;
And than set children count 0 to all parent id 2
UPDATE catalog_category_entity SET children_count = "0" WHERE parent_id =2;
