You will need to switch to the latest API. Stripe has made some changes and this means that the custom fields etc are shown on the Stripe popup. Can you please go to your Stripe Advanced Settings menu and make sure that you ‘do not’ have the legacy API enabled. Disabling that will ensure you are using the latest API. Then please go back to that page and take a look and see if it is working then. Let us know if the issue persists.
The screenshot on the addon page shows how the new API looks with custom fields: