The following are the symptoms of this issue:

• "Downloading.. 1%" message is displayed when accessing configuration from NetScaler Graphical User Interface (GUI).

  

• NetScaler GUI hangs at "Downloading... 1%" message when loading the Java applet.

• When you try to access the GUI from Internet Explorer, Firefox, and Chrome, the attempt is unsuccessful. After the Java version is downgraded to version 7 update 40, the issue still persists.

• When using some older builds such as NetScaler 10.0 74.4 you can get stuck at a "Downloading... 1%" message when accessing some configurations from the console.
   
• ​We can try with Java Version 7 update 21 and Java version 7 update 25 and check if that resolves the issue as the mentioned versions were compatible with 10.1.

Notes:

• This issue is a re-occurrence of an older issue with Java not working with the NetScaler GUI.

• This behavior was tested in NetScaler Build 10.1 121.10 and the same JRE error occurred.

To resolve this issue, complete one of the following methods:

Method 1

• Upgrade NetScaler version to NetScaler 10.1 125.8.nc or later.

Method 2

1. Download the latest version of Java.

2. Modify the Java settings as described in CTX200399 - Java Applets for NetScaler GUI Access Does Not Load.

3. Use Firefox and make sure to "Allow" the settings on the browser (look in both corners of the browser).

4. Change the URL of NetScaler in the browser, it should end with "gui" instead of "neo".

Citrix Documentation - Configuration Utility - Frequently Asked Questions