DJF He shouldn't complete the settings page. Sounds like he set up a new account.
Make sure he uses the same Google account that you sent the invite to. He's likely logged in on a different Google account. Or he accessed the link you sent after 6 hours, in which case it expires (and he then ended up setting up a new account).
I would suggest he Deletes his WW account (in Advanced, at the bottom) waits 20 mins and then send him a fresh share link, which he then should click on within 6 hours from you sending it.
