When the “Confirm details & pay 399” button is clicked, there is a loader for a brief moment, and nothing happens
If you are facing this problem, it is because of browser-related issues. You shall open a private/incognito window to see if it works. In case, you are using a mobile app, uninstall and reinstall the app to solve this issue.
If you are still unable to move forward, please send an email to firstname.lastname@example.org while sharing relevant screenshots.