Under MW 1.27 and earlier, the extension works like a charm, when upgrading to MW 1.28:
- Special:Category tree: interface changed and there is a message at the bottom 'Category ⧼rootcategory⧽ not found'. It was not there in 1.27
- there was message PHP Notice: Use of undefined constant CT_MODE_PAGES - assumed 'CT_MODE_PAGES' already during running of update it script. It refers to the definition $wgCategoryTreeMaxDepth = array(CT_MODE_PAGES => 3); in LocalSettings.php. as advised in mw:Extension:CategoryTree#Configuration. It was not there in 1.27.
- Downgrade to the version of extension generated for 1.27:
- Special:Category tree: Interface is to previous version.
- Category field is prefilled with ⧼rootcategory⧽, it was not there before.
- <categorytree mode=pages depth=3>Contents</categorytree> works fine under 1.27, under 1.28 it does not show the pages.