SQL-DATABASE ERROR

Database error in WoltLab Burning Board (): Link-ID == false, connect failed
mysql error: Connection refused
mysql error number: 2002
mysql version: unknown
php version: 5.6.40-57+0~20211119.60+debian9~1.gbp8a9bd1
Date: 05.05.2024 @ 23:04
Script: /memberslist.php?letter=&sid=cfe638b68ea6c527cf2737593c1b4734&order=DESC&sortby=userposts&page=1
Referer: http://stc-board.de/memberslist.php?letter=&sid=cfe638b68ea6c527cf2737593c1b4734&order=DESC&sortby=userposts&page=1