Problem with connection to mysql database configured but not up

I'm trying to upload a local system but it is not connecting to the database. I have already made the settings. I'll leave the error below if you can help me thank you.

hereandtheconfigurationinthedatabase

line code 124

    // Connect to the database and set the connection ID
    $this->conn_id = ($this->pconnect == FALSE) ? $this->db_connect() : $this->db_pconnect();

    // No connection resource?  Throw an error
    if ( ! $this->conn_id)
    {
        log_message('error', 'Unable to connect to the database');

        if ($this->db_debug)
        {
            $this->display_error('db_unable_to_connect');
        }
        return FALSE;
    }