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: 04.05.2024 @ 01:18
Script: /calendar.php?month=3&year=2024&sid=deb5bacd3b20b6e18eec4f1b89e15dc9
Referer: http://stc-board.de/calendar.php?month=3&year=2024&sid=deb5bacd3b20b6e18eec4f1b89e15dc9