What should I put in the PASSWORD_CLAIM_SECRET_BLOCK parameter with AWS Cognito User Pool using C #?

I'm registering users in AWS Cognito with C# based on the code provided in the following thread:

User management in AWS Cognito User Pool using C# and .NET

The way I'm registering a user is as follows:

CognitoUserManagement cognitoUserManagement = new CognitoUserManagement("default", RegionEndpoint.USEast1);
List<AttributeType> listAttribute = new List<AttributeType>();
await cognitoUserManagement.AdminCreateUserAsync(tbUserName.Text, pbPasswordUser.Password, _poolId, _clientId, listAttribute);

Works great until adminRespondToAuthChallengeRequest:

AdminRespondToAuthChallengeRequest adminRespondToAuthChallengeRequest = new
 AdminRespondToAuthChallengeRequest
{
    ChallengeName = ChallengeNameType.PASSWORD_VERIFIER,
    ClientId = appClientId,
    UserPoolId = userPoolId,
    ChallengeResponses = new Dictionary<string, string>
    {
        { "USERNAME", username },
        { "NEW_PASSWORD", password },
        { "TIMESTAMP",  DateTime.UtcNow.ToString("o") }
    },
    Session = adminInitiateAuthResponse.Session
};

In this part of the code, an exception is thrown stating that PASSWORD_CLAIM_SIGNATURE is required

I have been looking for what it can be about or what I should do but, I can not solve the problem.

Any comment or suggestion is welcome.

UPGRADE

It seems that it is the secret key or App client secret:

CognitoHashCalculator cognitoHashCal = new CognitoHashCalculator(); 
string cognitoHashCal = cognitoHashCal.GetSecretHash(username, appClientId, "YourAppSecretKey");

...

 ChallengeResponses = new Dictionary<string, string>
 {
     { "USERNAME", username },
     { "NEW_PASSWORD", password },
     { "TIMESTAMP",  DateTime.UtcNow.ToString("o") },
     { "PASSWORD_CLAIM_SIGNATURE",pass}
 },

This way you get to the last part of the code:

AdminRespondToAuthChallengeResponse adminRespondToAuthChallengeResponse = adminAmazonCognitoIdentityProviderClient
.AdminRespondToAuthChallengeAsync(adminRespondToAuthChallengeRequest)
.Result;

Here a new exception happens:

InvalidParameterException: Missing required parameter PASSWORD_CLAIM_SECRET_BLOCK