Hi Leonardo,
Currently, DATASTREAMWS does use HTTP in the endpoint. To work around the issue and use the HTTPS protocol through our interface, use the following code:
d = datastreamws("","","https://product.datastream.com/DSWSClient/V1/DSService.svc/rest/Token?username=user&password=pword")
d.URL = "https://product.datastream.com/DSWSClient/V1/DSService.svc/rest/GetData"
where user and pword are your username and password. After connecting with this syntax, you should be able to make historical requests.
Hope this helps!