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: 03.05.2024 @ 00:38
Script: /usercp.php?action=addsubscription&threadid=649&sid=ec1b95ad2fe9badcfc4389fdd1d831a4
Referer: http://stc-board.de/usercp.php?action=addsubscription&threadid=649&sid=ec1b95ad2fe9badcfc4389fdd1d831a4