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 @ 15:34
Script: /calendar.php?month=5&year=2024&sid=a89aa02f357d7e823d87a95b4ccb675c
Referer: http://stc-board.de/calendar.php?month=5&year=2024&sid=a89aa02f357d7e823d87a95b4ccb675c