I am trying to pre-order endwalker via https://store.eu.square-enix-games.com/

When I try to verify my payment info, this message appears:

"Please wait while your payment information is verified by our banking services. This may take up to 1 minute."

Followed up with: "An internal error has occured. Please try again in a few minutes."

This happens on my laptop and on my mobile phone. Both using Chrome as browser.

What can I do to fix this?