There are several things that you can double check before reporting a problem to support.
1. Check the Spam/Junk Folder - This is where email that are suspected as spam go.
2. Check the "Trash" Folder - When this setting has been setup on an email, suspected spam email are automatically deleted and can be found on this folder.
3. Double check that the email address is correct
4. When using a 3rd party program such as outlook, thunderbird, etc. Antivirus software usually plays a part in blocking incoming mail.
5. In some cases, web based email providers have different tabs. You may want to check on the tabs.
If all troubleshooting on your end is not successful, you can always email or call support with the date, time, event on the calendar and SH support can check logs to see if it actually sent. If the email has in fact been sent according to our records, then it will be something on the user's email settings that needs to be corrected.