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: 08.05.2024 @ 00:38
Script: /calendar.php?action=addevent&type=private&sid=e4c3e95f55780cb3390ed71294b93bc0
Referer: http://stc-board.de/calendar.php?action=addevent&type=private&sid=e4c3e95f55780cb3390ed71294b93bc0