Lead Autoresponder Not Sending all Emails

Lead Autoresponder Not Sending all Emails

The autoresponder that I have set up is sending the first two emails, but not the last one in the screenshot below. Many of our leads are not getting the 4th email, even after we wait the full amount of time. Here is a link: https://crm.zoho.com/crm/EntityInfo.do?module=Leads&id=920224000011148017 to an example lead who got the first two messages but not the day 10 survey email. Why is this?