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 @ 23:03
Script: /register.php?sid=a51560ca1a2db4345a28f486a585b24d
Referer: http://stc-board.de/register.php?sid=a51560ca1a2db4345a28f486a585b24d