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 @ 15:47
Script: /register.php?sid=4c633676c6dcad475fc9e55a93b4f3a5
Referer: http://www.stc-board.de/register.php?sid=4c633676c6dcad475fc9e55a93b4f3a5