Database connection problem

What could be the reason and where to fix it?
This message pops up when the installer tries to contact the database.

Cannot connect to database.n Access denied for user ‘xnova’@’localhost’ (using password: YES)

Added from comment.

Message: SQL Error: No database selected
Query Code: SELECT HIGH_PRIORITY * FROMconfigWHEREuni= '1';
File: /home/xnova/www_html/includes/classes/class.MySQLi.php
Line: 96
URL: http://xnova.gomel.by/index.php
PHP-Version: 5.2.4-2ubuntu5.17
PHP-API: apache2handler
2Moons Version:
Debug Backtrace:
#0 ./includes/classes/class.MySQLi.php(113): DB_mysqli->query('SELECT HIGH_PRI...')
#1 ./includes/GeneralFunctions.php(117): DB_mysqli->uniquequery('SELECT HIGH_PRI...')
#2 ./includes/common.php(90): getConfig(1)
#3 ./index.php(46): require('/home/xnova/www...')


Answer 1, authority 100%

The xnova user does not have access rights, if you administer the database yourself, then look towards setting the access rights of database users.

Alternatively, you could add a user, but allow him to connect only from a specific host.

Try connecting to the database, for example via phpmyadmin or the console, to check for access issues or problems with the installer.