I can't log into the apple shop

I can't log into the Apple Store. It is really about the problem of getting into the shop, for example. view my orders. When I click the button, I am redirected to a "Not Found" page without being able to log in.

I can log into the discussion platform here or into the icloud without any problems. But as soon as I want to order something or view my orders, I'm always redirected to 404 pages.

I'm a web software developer myself and I've tried everything I can think of: clear browser cache, open private tab, use a different browser, try with a Windows device, etc. It doesn't seem to be a local problem, but somehow account-specific?

Here I will eg. forwarded:

https://secure5.store.apple.com/shop/order/list

Does anyone have an idea what it could be?