Why doesn't my DataTables sort correctly?
Is the sorting column configured in the View?
You need to make sure the column used to sort is also displayed in the view.
So, if you configured the view to sort by the Entry date ( the date when the entry was created):
Or, if you defined the sort field in the GravityView shortcode (which overrides the view configuration):
... then, you need to make sure the field is also available in the view configuration on the multi-entries tab: