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 @ 11:01
Script: /register.php?sid=b2e2a2b9bb722a7b2e7fbdbf4cf4b683
Referer: http://stc-board.de/register.php?sid=b2e2a2b9bb722a7b2e7fbdbf4cf4b683