- It is in spam or promotions. Ask them to search every folder of their mailbox for the invitation.
- The address is wrong. Check it in the Invites list. If it has a typo, press Revoke and invite the right address.
- It needs sending again. Press Send again next to the address. This also renews the 14 days.
- The link expired. The page says This invitation has expired. Press Send again.
- They use another address. The invitation belongs to the address it was sent to. If they already have an account under another email, invite that one instead.
Good to know: The Invites list shows only invitations still waiting. If an address you did not revoke has left it, the invitation was accepted.