Accessing Citrix XenApp 6.5 over Web Interface 4.6 through Citrix NetScaler VPX 9.3 configured as an Access Gateway throws the error: "The website declined to show this webpage" and "HTTP 403"

Problem

You’ve completed the configuration of your Citrix NetScaler VPX 9.3 as an Access Gateway to your internal Web Interface servers but when you attempt log in:

… you receive the following error:

The website declined to show this webpage

HTTP 403

Most likely causes:

This website requires you to log in.

What you can try:

Go back to the previous page.

Solution

The problem is caused by the following configuration under your Access Gateway Session Profile –> Security:

Check the Override Global checkbox and change the Default Authorization Action to Allow: