Sometimes zap tasks will halt midway through running- usually due to a failed search step. Because this doesn't always mean something went wrong, it's not counted as an error and you won't get a normal error alert from Zapier.
This zap is quite simple to use. By default, the zap will trigger whenever any zap task in your account is halted.
Depending on your needs, you can use the three dropdowns on the trigger tab to narrow the circumstances in which the zap will trigger. "Account" lets you restrict the trigger to only zaps on a certain account (if you're part of multiple teams). "Folder" lets you restrict to zaps in a certain folder. Finally, "Zap" lets you target a specific zap.
Next you want to send the alert. This can be a simple email, or something else like an SMS, or Slack alert for example. You can map fields from the trigger to make it easier to work out which zap went wrong. You can access data like the zap name, the reason for the halt and a link to the zap's log.