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 @ 17:54
Script: /usercp.php?action=addsubscription&threadid=827&sid=ec5ed24ea886f1d25cd22b0360cb92ec
Referer: http://stc-board.de/usercp.php?action=addsubscription&threadid=827&sid=ec5ed24ea886f1d25cd22b0360cb92ec