What triggers a checklist task that is on delay? Also, what triggers reminders set on the tasks?

I have a journey that is assigned to new hires when their new hire record is created, but we don't want a certain task to trigger until one day after. I have a 1-day delay duration set for that task, however, I'm not receiving the notification for it in my test environment. Is there a process that needs to be triggered in order for it to send?