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: 05.07.2022 @ 11:53
Script: /calendar.php?sid=ba67df42fe95c278ec7058e837eb47e0
Referer: