For users
For security reasons, invites to Penneo are only active for 14 days. If you have received a invite which have expired you should contact your administrator, who can send you a new invite.
For administrators
If you have a user with an invitation that have expired, you need to send a new invitation. The way you do this, is by deleting the user and then creating them again. When you do this a new invitation will be send out.