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 @ 00:39
Script: /board.php?boardid=55&daysprune=1000&sortfield=starter&sortorder=ASC&sid=84814b448153e428b6e22ba3d31d3f12&page=1
Referer: http://stc-board.de/board.php?boardid=55&daysprune=1000&sortfield=starter&sortorder=ASC&sid=84814b448153e428b6e22ba3d31d3f12&page=1