Pop up workflow justification is not opening the portal

Hello, I am using the MSS portal for approval workflow. The Workflow user has the decision In which I modeled for rejecting the mandatory text option (Justification) to be placed When the user choice this option.

  I run the Workitem using the SAP / HCM, the Workflow ask for justification in the mandatory PopUp after the rejection option is selected, but if I run the Workitem using MSS Portal, the text option is mandatory after rejecting the task is not displayed.

Any suggestion?

Thanks a lot.