SSL Issues Preventing Access to Website

I just bought a new MacBook Pro (Catalina 10.15.6) that replaced my 2013 Macbook Pro (Sierra 10.12.6). The transition is complete except for one persistent problem. I can't access the puzzles on the "Cracking the Cryptic" website that I love. I can access all the other websites that I typically visit. I have tried to access puzzles on the site using both Chrome and Safari, and I get the same thing. The browsers attempt to load the site for exactly 2 minutes, and then display the statement "Sorry, it looks like that puzzle doesn't exist!" However, when I go to View/Developer/Javascript Console, I get several instances of the following, "Failed to load resource: net::ERR_CERT_AUTHORITY_INVALID". The puzzles load just fine on my old Macbook Pro and on my wife's Macbook Air. When I click on the padlock to the left of the browser title bar, it indicates that the website's certificate is issued by Globalsign and that it is valid and up to date. I have tried reloading Chrome, and clearing the browser's history/cookies/cache. Any suggestions?