I found the answer. The SetFieldProperty command was using PdfFormField.FLAGS_HIDDEN and it should be using PDfAnnotation and "setflags' instead.
So
form.SetFieldProperty(dictionaryEntryPrintButton.Keys(0), "setfflags", PdfFormField.FLAGS_HIDDEN, Nothing)
Becomes
form.SetFieldProperty(dictionaryEntryPrintButton.Keys(0), "setflags", PdfAnnotation.FLAGS_HIDDEN, Nothing)
And I don't need the RegenerateField command.