It looks like the issue is that the <span class="validationMessage" data-bind="validationMessage: dueDate"></span>
doesn't get automatically generated for knockout-kendo tags. Just add a tag per knockout-kendo element, ex:
<input data-bind="kendoComboBox: {
data: myOptions,
value:myOptionId,
dataTextField: 'MyOptionName',
dataValueField: 'MyOptionId'}"/>
<span class="validationMessage" data-bind="validationMessage: value:myOptionId"></span>
<input data-bind="kendoDatePicker: {value: dueDate}"/>
<span class="validationMessage" data-bind="validationMessage: dueDate"></span>
Remember to put before your view model:
ko.validation.configure({
registerExtenders: true,
messagesOnModified: true,
insertMessages: true,
parseInputAttributes: true,
messageTemplate: null
});
ko.validation.registerExtenders();