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  : Sunday, December 3rd 2023 @ 12:47:01 AM
Error Date    : Sunday, December 3rd 2023 @ 12:47:09 AM
Script        : http://forum.ucool.com/forumdisplay.php?do=markread&markreadhash=1695913312-a66eb06e3c6f1974f7ad76679094629a7c1853c7
Referrer      : 
IP Address    : 44.220.249.141
Username      : 
Classname     : vB_Database
MySQL Version :