Follow up timer feature allows you to nudge a user after certain duration of time within 24 hours of last incoming message from the user. We have to build two automations in order to correctly set up a follow up timer
Automation 1: Create a follow up timer:
You have to first define your timer and what keyword should trigger that timer.
Add automation >> message received >> add type of trigger>> add keyword that should trigger a follow up timer >>Add action>>set a follow up timer>>Give your trigger a name and countdown timer >>Activate
Automation 2: Call your follow up timer:
You have to define what happens when the follow timer countdown ends.
Add Automation >>Follow up timer completes >> Select the timer >> Add your action.
For detailed info refer this https://learn.turn.io/automation/how-to-setup-a-follow-up-timer