Database error in vBulletin :

mysql_connect(): Can't connect to MySQL server on 'mysqlucoolbbsmaster' (104)
/data/product/ucool/production/bbs/a/includes/class_core.php on line 317

MySQL Error   : 
Error Number  : 
Request Date  : Friday, December 1st 2023 @ 01:18:25 AM
Error Date    : Friday, December 1st 2023 @ 01:18:33 AM
Script        : http://forum.ucool.com/memberlist.php?ltr=I&pp=30&sort=username&order=asc
Referrer      : 
IP Address    : 18.206.12.157
Username      : 
Classname     : vB_Database
MySQL Version :