Your task history show all the tasks your Zaps have tried to run. Each task in your task history will have one of five task statuses. Failed or unsuccessful tasks can be manually or automatically replayed.
Replaying a Zap only executes failed tasks, not successful tasks. For example, a Zap might have two actions: 1. Send an email, and 2. Add a spreadsheet row. If the Zap runs and successfully sends the email, but fails to add the spreadsheet row, replaying the task will only attempt to add the spreadsheet row again, not send the email again.