Invalid Checksum issue


I am receiving the below error when I try to generate a session. Could you please guide?

Authentication failed: Invalid `checksum`.
Fatal error: Uncaught KiteConnect\Exception\TokenException (403) 'Invalid `checksum`.' thrown in /path/KiteConnect.php on line 1652.

Below is the snippet of my code:

require_once '../vendor/autoload.php';
use KiteConnect\KiteConnect;

$request_token = $_GET['request_token'];

//echo $request_token."";

// Initialise.
$kite = new KiteConnect($api_key);

// Assuming you have obtained the `request_token`
// after the auth flow redirect by redirecting the
// user to $kite->login_url()
try {
$user = $kite->generateSession($request_token, $api_secret);
echo "Authentication successful. \n";
} catch(Exception $e) {
echo "Authentication failed: ".$e->getMessage();
throw $e;

echo $user->user_id." has logged in";
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