This could be because it has expired. The link is valid for 20 minutes; if you haven’t clicked it within that time frame you can open the app and press send again.
Alternatively, when a new validation email is sent, the previous one becomes redundant, it may be that you’ve re-sent the link; in the meantime, the original one arrived that is now expired.
If you are having trouble we recommend deleting all emails from firstname.lastname@example.org from your inbox and junk folder and then resend a new link. Wait for that one to arrive and press it.
If you continue to have problems, contact a member of the centre management team who will be able to do it manually for you.
Once you have clicked the validation link just press ‘I have clicked the link’ and you’re in