PAM 4.1 SP1 comes with an example in the Out-of-the-Box content. It's under /PAM_PredefinedContent/User Interaction Forms/01 Send Task URL in the Library.
In the example, you will find the correct format for the URL that is sent as part of the Send Email operator, Message field. The correct format for the URL is formed like
getOrchestratorURL() + 'itpam?ROID=' + Process.Assign_User_Task_1.TaskID + '&page=replytask'