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: 11.05.2024 @ 13:33
Script: /usercp.php?action=addsubscription&threadid=187&sid=55f9e2fb714c7c80b2c35c61a0d564fb
Referer: http://stc-board.de/usercp.php?action=addsubscription&threadid=187&sid=55f9e2fb714c7c80b2c35c61a0d564fb