Drupal8 + Plesk: User path missing from cmsRootPath()
The cmsRootPath() is not able to get absolute path, specifically the user folder portion of the path on Plesk.
This might be caused by multisite setup, function being insufficient or permission.
To fix CRON for plesk the following needs to be changed
vendor/civicrm/civicrm-core/CRM/Utils/System/Drupal8.php at line 441:
-return $civicrm_paths['cms.root']['path'];
+return realpath($_SERVER["DOCUMENT_ROOT"]) . '/'.array_slice(explode('/', $civicrm_paths['cms.root']['path']), -1)[0];The cause is that in Plesk all files and directories under a domain document root directory should belong to psacln group and to the sysuser user. Where sysuser is a user of a corresponding subscription.
CIVICRM Cron only expects a chown -R www-data|psaserv .
The way to set correct permission is a correct way to fix the issue for subdomain. This is described in the article above in step 3. https://support.plesk.com/hc/en-us/articles/115004094934