This issue is usually caused by one of the following:
The email has been directed to the investor's junk or spam folder. We would advise them to check these folders for an email from notifications@exemptedge.com and add us as a trusted contact.
The Investor is using a company email address or an email address tied to a private domain. These domains typically use much stricter firewalls so it's possible that our emails are being blocked. We suggest that the investor contact their work's IT department in order to see if our emails may be caught in the firewall and ask that they add notifications@exemptedge.com as a trusted contact. Alternatively, they can modify their email address to use a public domain email address as these do not restrict our emails.