Darn!  Don't get discouraged, any number of things might be happening.  For example:

• The person you are sending it to may have an outdated email in their profile, so it never reached them.
• They don't check their email very often and haven't seen your request yet.  
• They didn't recognize the sender "[email protected]" and ignored the email.  
• The request went into their spam folder, and they didn't see it.

The best way to make sure messages get through is to encourage everyone to keep their profiles updated.