How can I Deserialize MessagePack from Json (via Python) with a DateTime property?

Question

I'm trying to deserialize a MessagePack message generated from a python client to a .net object. Running into some trouble with DateTimes. Interestingly staying in the C# arena it doesn't work either.

Newtonsoft is able to deserialize the json correctly. Although MessagePack's ToJson returns valid Json, deserializing the object fails.

[DataContract]
public class TestClass
{
    [DataMember]
    public string TestPropertyA { get; set; }
    [DataMember]
    public string TestPropertyB { get; set; }
    [DataMember]

    public DateTime EventTimeStamp { get; set; }
}

        //Move from Json string to an object
        String jsonStringFromPython = "{\"TestPropertyA\":\"Hello\",\"TestPropertyB\":\"World\",\"EventTimeStamp\":\"2019-05-02T16:04:30.7812850Z\"}";
        TestClass anObject = JsonConvert.DeserializeObject<TestClass>(jsonStringFromPython);

        //Generate byte arrays for Messagepack
        Byte[] arrFromAString = MessagePackSerializer.FromJson(jsonStringFromPython);
        Byte[] arrFromAnObj = MessagePackSerializer.Serialize<TestClass>(anObject);
        CompositeResolver.RegisterAndSetAsDefault(PrimitiveObjectResolver.Instance, ContractlessStandardResolver.Instance);

        //Message pack understands the object-generated byte array
        var backtoobject = MessagePackSerializer.Deserialize<TestClass>(arrFromAnObj);

        //Message pack DOES NOT UNDERSTAND the string-generated byte array and fails with code is invalid. code:188 format:fixstr'
        var backtoobject2 = MessagePackSerializer.Deserialize<TestClass>(arrFromAString);

The last line of code above fails, but all works flawlessly if I drop the DateTime property from the string/object.