Cannot do CSS edit on the check out page

Hi Team,

I would like to share the problem that me and my team are experiencing. 
Previously we have installed this plugin https://www.airwallex.com/sg/business-account/payment-links-plugins for this website https://www.pierzel.com/

Unfortunately, it seems like on the check out page here: https://prnt.sc/6Lcyl9cDJu0i is kinda different from the screenshots from the plugin here: https://wordpress.org/plugins/airwallex-online-payments-gateway/ and we cannot edit this via css.

When we installed the plugin: https://prnt.sc/WUgPRMB0GGIq it looks like this.

Thanks,

The page I need help with: [log in to see the link]