urlread get method problems when passing header arguments

Hello, this problem arises from using an API (source: https://bittrex.com/home/api)

The point is when authenticating with Post method I haven't found problems. However Bittrex asks to do it so via Get method.

Based on instructions and python source code here is my own code (applied for 'getopenorders' method-parameter):

if true
  % code
url_base = 'https://bittrex.com/api/v1.1/market/getopenorders';
body = [url_base,'?apikey=',apikey,'&nonce=',nonce];
sign = hmac(secret_key, body, 'SHA-512');
json = urlread( body, 'Get', {'apisign', sign} )

end

urlread successfully return a string, but contains an API error message:

{"success":false,"message":"APISIGN_NOT_PROVIDED","result":null}

With other API interfaces based on 'Post' method the arguments were successfully passed, but not in this case.

If there is someone strongly experienced who dares to suggest solutions I will be deeply thankful!

Regards José

[José Crespo Barrios]

After diving few days in the topic, it seems to be that MATLAB is uncapable of passing header-parameters via get method. Please I kindly ask to correct me if I were wrong on this point. Thanks