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: 01.05.2024 @ 16:24
Script: /usercp.php?action=addsubscription&threadid=710&sid=0956ebd6f7e014caf9612fcfb3b857cf
Referer: http://stc-board.de/usercp.php?action=addsubscription&threadid=710&sid=0956ebd6f7e014caf9612fcfb3b857cf