Overview: The user hasn’t received an event open email.

• The email is going to the user’s junk mail. Have the user check their Spam and Junk email folders (as the email may have gotten re-routed there). The user should also whitelist the email address that future emails will be sent from.  Whitelisting instructions can be accessed here.
• The registrant has used a dummy or invalid email address when registering. The email address should be viewed in the tenant and changed to the correct email address. If the email address appears to be correct, make sure there are no extra spaces that may have been appended to the end of the email in error.