Send from Triggering User not working


I am tasked to create a routing approval Smartsheet.

One of the steps is to get Smartsheet to send an email to a Leader and the Leader will reply via email instead approving via Smartsheet due to audit purposes where the email approval needs to come from the Leader mailbox.

I tried using the “Send from Triggering User” in Alert Someone (see screenshot below). I got my colleague EH to submit the request but when I use the email to reply to, it is replied to me (From: ATan via Smartsheet <>) instead of the Triggering User who is EH. I have set the form where a user needs to login.  

How can I resolve this?