Unable to download Easyjet Plus card from their email to my apple wallet

Hi, I've just joined easyjet plus and have tried to download the membership details to my apple wallet from the email. But when I try to do it it comes up with a message that says, "This connection is not private. This website may be impersonating 'wallet.pct.tech' to steal your personal.....etc.." When I click on 'Show Details' it says things like, "safari warns you when a website has an expired certificate" and, the certificate has expired 39 days ago, and, this may have happen if the website is misconfigured, an attacker has compromised your connection, or your system clock is incorrect (the clock is fine), To learn more you can 'view the certificate' (made no sense to me). If you understand the risks involved, you can 'visit this website' (haven't been brave enough to click on that one!!)" I would be very grateful if anyone can help me with this problem.