Well, in that page you should also see an ‘Add to Cart’ button with a price tag. This page is only to buy the update. You’ll receive an activation code to unlock the new license by email.
The ‘immediate donwload’ is already available from the Steinberg Download Assistant or directly from the website. But you need the activation code to unlock it.
The situation here on Planet Palmer is extremely grave. Firstly we have the Brexit calamity, secondly the corona virus is creeping up on us and most worrying of all the Wavelab upgrade page does not appear to be functioning!
I fear that our chances of survival are currently very slim.