If you would like to create a reminder to send requesters who have not opened their email or replied to a ticket that is less than solved status a reminder you can create the following automation:
Set ALL conditions to:
- Ticket tags contain at least one of the following tags: mrr-unread.
- Ticket hours since pending is greater than 12.
- Ticket hours since the requester update is greater than 12.
- Ticket status is less than solved.
Set ACTION to email the requester with the desired content.
This automation will fire when there is an unread ticket tag, the ticket has been in pending status or has not had a requester update in 12 hours AND either the ticket is in less than solved status the automation should run on the 13th hour executing the action you have set.