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: 28.04.2024 @ 14:03
Script: /usercp.php?action=addsubscription&threadid=880&sid=e390929affa6b63479dd378f3b7a699a
Referer: http://stc-board.de/usercp.php?action=addsubscription&threadid=880&sid=e390929affa6b63479dd378f3b7a699a