The button with link "Login with OIDC" (bottom right) is only visible in the storage area index page, not in the specific storage area pages.
E.g.:
you see it here
https://xfer-archive.cr.cnaf.infn.it:8443/
but you don't see it here
https://xfer-archive.cr.cnaf.infn.it:8443/cta-lst
(being the latter an error page Forbidden...)