Thank you @peeld,
COuld you please check one more think… Please make sure you don’t have an old wpDiscuz template file in your current active WordPress theme folder. Use the Theme Editor and check current active theme or in the child theme folder this file:
/wp-content/themes/mytheme/wpdiscuz/class.WpdiscuzWalker.php
Maybe your wpDiscuz was customized and the customized version was put in active theme or in active child theme folder to make it save when you update wpDiscuz. If you find this file you should download it, then delete it to allow wpDiscuz load its new template files. Old template files are not compatible with new versions of wpDiscuz.