notification not able to receive when the use replied to active ticket

[Yougander patel]

A ticket is created.The user receives a notification email.The user replies to that email.The reply is captured in the ticket's activity log.However, the assigned to person does not receive a notification about that reply. and not updating in additional comments 

[Mark Manders]

One: what logs do you get from your gs.info?

Two: why do it like this? Why not add it as an event (or a notification) directly on the record itself? 

Three: your 'gr.assigned_to.toString()' will almost certainly return the sysid of the user, not the email address.