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: 09.05.2024 @ 23:25
Script: /calendar.php?month=5&year=2024&sid=ad9dae502dd70949382f75ffff311893
Referer: http://stc-board.de/calendar.php?month=5&year=2024&sid=ad9dae502dd70949382f75ffff311893