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: 02.05.2024 @ 17:36
Script: /register.php?sid=7684d071389f9f74ca67cd5ae9d9c654
Referer: http://stc-board.de/register.php?sid=7684d071389f9f74ca67cd5ae9d9c654