I have emailed them and went to the facebook page but there wasn't a way to leave a message there
This has happened to a few people as well as magazines without a code number or too blurred to read (printing errors).
You can certainly send them a message on the Facebook page as I've done so to report spammers etc while others have been asked by That's Life to message their details there to get a new code.
They have also given codes via phone and email and have been very prompt.
If you can't see the message box at top have you Liked and subscribed?