Recently upgraded NetScaler 10.5 to 11. Upgrade completed fine but when accessing the NetScaler Gateway portal nothing other than the below was presented. No logon screen. Just a blank white page. Same result using multiple web browsers. This also happened on a seperate occasion when there was a power cut that affected a NetScaler MPX.
To fix I copied the vpn folder from a different working NetScaler (same major build0) and used this to replace the one on the broken NetScaler. The directory you should look for is /netscaler/ns_gui/vpn.
After that the correct logon screen appears again and the problem is resolved. I’m not sure why the index.html page seemed to have been corrupted. It could have been caused by the upgrade or if someone had badly modified it in the past and it was incompatible with NSv11.
Note: When you reboot NetScaler, every file and folder gets recreated unless they are located in the /flash/ or /var/ directories. This may mean that when you reboot NetScaler the corrupt index.html returns. To make sure the good copy of the vpn folder is copied after restart follow the below:
Copy a good known copy of the vpn folder to /var/ on the affected NetScaler appliance. Before copying the folder rename it to vpnworking or similar.
Navigate to /nsconfig/ and double click the file rc.netscaler.
Add a line with command cp /var/vpnworking/* /netscaler/ns_gui/vpn/. This ensures the vpnworking foler is copied to /netscaler/ns_gui/vpn/ once ns.conf is loaded. Any folders/files with the same name within the corrupt vpn folder are overwritten.