A couple of additional revisions

apps/openassessment/templates/openassessmentblock/response/oa_response_closed.html

@@ -16,7 +16,7 @@
 {% block body %}
 <div class="ui-toggle-visibility__content">
   <div class="step__instruction">
-      <p>You did not complete this step of the problem before its due date.</p>
+      <p>You did not complete this step before the problem's due date.</p>
   </div>
 </div>
 {% endblock %}