I added a user to my account, but their email welcome link has expired

For security reasons, password re-set and creation links in user emails last for 15 minutes before needing to be re-set. If your new user does not click their link in time, you can generate a new email / link for them by clicking on the email icon in their row on your user admin page:

Alternatively, the user can themselves go to https://www.seatrobot.com, click the 'Login' link, and then select 'forgot password'. They will be prompted to add their email address and they will receive a password-reset email allowing them to create a password and login for the first time.