My account page doesn't show an option for a mobile app setup. It only has 2 options: Setup a new physical security key, and link a previously setup physical security key.
It did have that option originally, but instead of showing me a code, it showed me my email address. Refreshing the page sent me back to the login screen and now that page isn't available anymore.
This one I have not seen. Beyond saying to contact customer service, I am unsure what you could do. Sorry.