Fatal error: Link-ID == false, Verbindung fehlgeschlagen

Error Message: Link-ID == false, Verbindung fehlgeschlagen
Error Code: 1045
SQL Type: Database
SQL Error: Access denied for user 'web621'@'localhost' (using password: YES)
SQL Error Number: 1045
SQL Version:
File: /var/www/vhosts/web621.webbox442.server-home.org/html/v2/lib/database/Database.class.php (76)
PHP Version: 5.6.36
GUI Version: 2.6.5
DB Build: 1063
Date: Sun, 27 May 2018 09:22:45 +0000
Request: /
Referer:

Stacktrace:

#0 /var/www/vhosts/web621.webbox442.server-home.org/html/v2/lib/database/Database.class.php(60): Database->connect()
#1 /var/www/vhosts/web621.webbox442.server-home.org/html/v2/lib/database/Database.class.php(517): Database->__construct(...)
#2 /var/www/vhosts/web621.webbox442.server-home.org/html/v2/acp/inc/init.php(107): require_once('/var/www/vhosts...')
#3 /var/www/vhosts/web621.webbox442.server-home.org/html/v2/global.php(35): require_once('/var/www/vhosts...')
#4 /var/www/vhosts/web621.webbox442.server-home.org/html/v2/index.php(10): require_once('/var/www/vhosts...')
#5 {main}