If Social Login (zkLogin) isn't responding, it is usually due to a network constraint. Depending on the location from where you are accessing the Slush app, it might be the case that you first need to connect to a secure VPN service before accessing the app. It could also be the case that your browser is blocking the authentication pop-up.
Try clearing your browser cache and cookies, make sure that pop-ups are allowed in your browser settings, and try logging in again.