Congratulations, you have successfully discovered that the public hostname is public.
Looking for /login? Cute.
You can keep guessing paths if you like, but the answer will remain the same: staff access is at https://staff.nexus.tboxtech.com/.
If you were hoping this page would accidentally expose the staff login, today is not your day.
Before Nexus even considers showing you the next authentication step, TLS wants to see a valid client certificate.
Get past that securely, then we can talk about the rest.