Deserializing object with dynamic property won't work

Question

I'm having troubles with deserializing an object with a dynamic field, which will hold different api responses. This is how it looks like:

public class ServiceCallResult
{
    private dynamic _dataObject;
    private Type _dataType;
    public Type DataType
    {
        get
        {
            return _dataType;
        }
        set
        {
            _dataType = value;
        }
    }
    public dynamic DataObject
    {
        get
        {
            return _dataObject;
        }
        set
        {
            _dataObject = value;
        }
    }
    public string ErrorMessage { get; set; }
    public bool Success { get; set; }

    public ServiceCallResult()
    {
    }
    public ServiceCallResult(Type type, dynamic obj)
    {
        DataType = type;
        DataObject = obj;
        Success = true;
    } 
}

And it could hold an object like this:

public class ApiPractitioner
{
    public int Id { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string CompanyName { get; set; }
    public int CVR { get; set; }
    public string Address { get; set; }
    public short ZipCode { get; set; }
    public string City { get; set; }
    public string Phone { get; set; }
    public string Email { get; set; }
    public string Password { get; set; }
    public string Description { get; set; }
    public byte[] ProfileImage{ get; set; }
    //[JsonIgnore]
    //public List<ApiPractice> Practices { get; set; }
    //[JsonIgnore]
    //public List<ApiClient> Clients { get; set; }
}

But when deserializing with this code:

var req = new RestRequest("practitioner/createpractitioner", Method.POST);
req.RequestFormat = DataFormat.Json;
req.AddBody(prac);

var response = _client.Execute<ServiceCallResult>(req);
ServiceCallResult td = new JsonDeserializer().Deserialize<ServiceCallResult>(response);

It ends up with a "MissingMethodException" in mscorlib.dll, additional information is "An abstract class can't be created". The response object has the json content but there's and exception like the one when I use the JsonDeserializer and I can't figure out what's going on, I've searched for hours on Google and tried different suggestions with no luck. Anyone tried the same with a dynamic property?

I'm using RestSharp for the json handling.

Best regards Benjamin

After a little enlightment from Michael I've changed my ServiceCallResult to this:

public class ServiceCallResult<T> where T : BaseApiResponse
{
    public T DataObject { get; set; }
    public string ErrorMessage { get; set; }
    public bool Success { get; set; }

    public ServiceCallResult()
    {
    }
    public ServiceCallResult(T obj)
    {
        DataObject = obj;
        Success = true;
    } 
}

And all my api responses inherits from BaseApiResponse.