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: 05.05.2024 @ 18:08
Script: /register.php?sid=9bc95134d2e85e9e2d53e72152a3a06c
Referer: http://stc-board.de/register.php?sid=9bc95134d2e85e9e2d53e72152a3a06c