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: 06.05.2024 @ 18:19
Script: /attachment.php?attachmentid=1164&thumbnail=1&sid=090f2b391ee2655b23194b81453bb4d3
Referer: http://stc-board.de/attachment.php?attachmentid=1164&thumbnail=1&sid=090f2b391ee2655b23194b81453bb4d3