When an invite is sent to mobile phone we look to see when it has been delivered so that we can update the status on the website. Its possible the invite can not be delivered for several reasons, for instance the phone number that you entered is incorrect or the phone has been switched off for a couple of days.

If this happens you should check with the person you are inviting, to make sure you have the correct number, and their phone is switched on and ready to receive messages. Then you can send a new invite to them from the website.