When a new account has been created the registration link to complete the sign-up is only valid for 96 hours. If this link expires and needs to be re-sent please contact an administrator in your company so they can trigger a new link for the user in case that happens. The below steps are what the admin needs to be in order to re-send this registration link.
1. Go to Company → Users and you will see which user still has a registration pending and click on the edit icon on the right
2. Under Personal info and in the section Login you will see a blue box where you can press the button "Resend registration link to: email"
3. A new email should now be triggered to the user's security email. Sometimes it may take up to 10 minutes for the email to appear in the mailbox.