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: 08.05.2024 @ 08:09
Script: /usercp.php?action=addsubscription&threadid=865&sid=2149138d6085fb4204a5680e2bb84dae
Referer: http://stc-board.de/usercp.php?action=addsubscription&threadid=865&sid=2149138d6085fb4204a5680e2bb84dae