How do I fatal error: uncaught mysqli_SQL_exception

Fatal error: Uncaught mysqli_sql_exception: Access denied for user 'username'@'localhost' (using password: YES) in E:\New folder\htdocs\Online Property Sales System\Src\html\register.php:10 Stack trace: #0 E:\New folder\htdocs\Online Property Sales System\Src\html\register.php(10): mysqli->__construct('localhost', 'username', 'password', 'Property_Lanka') #1 {main} thrown in E:\New folder\htdocs\Online Property Sales System\Src\html\register.php on line 10

<?php
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "Property_Lanka";

// Create connection
$conn = new mysqli('localhost','root','','Property_Lanka');
// Check connection
if ($conn->connect_error) {
  die("Connection failed: " . $conn->connect_error);
}

$sql = "INSERT INTO MyGuests (`fname`, `lname`, `Pass`, `mno`, `dob`, `email`)
VALUES('$fname','$lname','$pass','$mno','$dob','$email')";

if ($conn->query($sql) === TRUE) {
  echo "New record created successfully";
} else {
  echo "Error: " . $sql . "<br>" . $conn->error;
}

$conn->close();
?>