- Check the event
Is the attachment added to the event you didn't receive? - Check message settings
Verify that the attachment settings on your calendar are turned on. - Check for emails
Check to see if you received the invitation in your email account instead. - Check the organizer
Ensure that the organizer has the same email address that is associated with their calendar. - Verify AllowForwardingExternalAttendees
Verify that AllowForwardingExternalAttendees is set to true.