AWS Cognito Custom SMS Sender: Decrytping code

When trying decrtypt the code the AWS Encryption SDK throws below exception.

AWS.EncryptionSDK.AwsEncryptionSdkException: Unsupported Version value.

Below is the code used to decrypt.

 string keyArn = "**************";    

var materialProviders =
                    AwsCryptographicMaterialProvidersFactory.CreateDefaultAwsCryptographicMaterialProviders();
            // Configure the commitment policy on the AWS Encryption SDK instance
            var config = new AwsEncryptionSdkConfig
            {
                CommitmentPolicy = CommitmentPolicy.REQUIRE_ENCRYPT_ALLOW_DECRYPT
            };
            
            var encryptionSdk = AwsEncryptionSdkFactory.CreateAwsEncryptionSdk(config);

            // Instantiate the keyring input object
            var kmsKeyringInput = new CreateAwsKmsKeyringInput
            {
                KmsClient = new AmazonKeyManagementServiceClient("******", "**********"),
                KmsKeyId = keyArn
            };

            var keyring = materialProviders.CreateAwsKmsKeyring(kmsKeyringInput);

            using (var stream = GenerateStreamFromString(smsSenderEvent.Request.Code))
            {

                var decryptInput = new DecryptInput
                {
                    Ciphertext = stream,
                    Keyring = keyring
                };

                logger?.LogInformation("UserManagementService: SendInvitationSms Before Decrypt");

                var decryptOutput = encryptionSdk.Decrypt(decryptInput);

                logger?.LogInformation("UserManagementService: SendInvitationSms After Decrypt");

            }

Below is used to convert code to memory stream.

public static MemoryStream GenerateStreamFromString(string s)
    {
        var stream = new MemoryStream();
        var writer = new StreamWriter(stream);
        writer.Write(s);
        writer.Flush();
        stream.Position = 0;
        return stream;
    }

Appreciate any help on this issue.