Issue:
After upgrade, when you open the netscaler gateway url, instead of showing the username and password page, it immediately shows a white page.

Solution:

This is mostly seen when upgrading from 10.5 to 11. From a working netscaler copy the folder, /netscaler/ns_gui/vpn and replace this folder on your current netscaler. Refresh the gateway vip url. It should work. You can also check the gateway url. If it is /vpn/index.html, check the index.html file if you’re using a custom theme. If it is portal theme, it will be /logon/LogonPoint/index.html. Check these html files if they are corrupted.