When I am creating a new site thru ISPConfig, it is not creating the web directory or the link to it. I'm running ver 3.1.2p3 of ISPConfig on a Ubuntu server, ver 18.04.5 LTS.
Please run thze command php --version and post the output. I guess you might have changed your system PHP to PHP 8.
PHP 8.0.7 (cli) (build: Jun 4 2021 21:25:51) ( NTS ) Copyright (c) The PHP Group Zend Engine v4.0.7, Copyright (c) Zend Technologies with Zend OPcache v8.0.7, Copyright (c), by Zend Technologies
PHP 8 is not supported as system PHP version, that's why it does not work. see here: https://www.howtoforge.com/community/threads/please-read-before-posting.58408/ chapter 'Panel not showing up' to fix this.