Error 400 - Bad request with account evaluation

Hello everyone,
I created an account evaluation for MapPoint, now I have developed a 
class for geocoding but when I request the server responds with an error 
400 Bad Request.

The code is as follows:

             Address myIndirizzo = new Address();
             myIndirizzo.PrimaryCity = indirizzo;

             FindOptions findOptions = new FindOptions();

             FindAddressSpecification findAddressSpecification = new 
FindAddressSpecification();
             findAddressSpecification.InputAddress = myIndirizzo;
             findAddressSpecification.Options = findOptions;
             findAddressSpecification.DataSourceName = ".....";

             findAddressSpecification.Options.ResultMask =
         FindResultMask.RooftopFlag |
         FindResultMask.LatLongFlag |
         FindResultMask.EntityFlag |
         FindResultMask.MatchDetailsFlag |
         FindResultMask.AddressFlag;
             FindResults myFindResults=null;
             try
             {
                 myFindResults = 
findService.FindAddress(findAddressSpecification);
             }
             catch (Exception e)
             {
                 Console.Write(e.Message);
             }