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Last update: . Author: Alan Carson .

Internet Information Services (IIS) Installation Issues - GSX Analyzer: HTTP 500.21 Internal Server Error

This article explains how to enable the missing Microsoft Internet Information Server (IIS) components generating the 500.21 error when attempting to launch GSX Analyzer for the first time.

The IIS installation wizard does not include all features required by GSX Analyzer during default install, so they must be manually added by selecting them during a custom installation from the Application Development Features in the IIS options.

GSX Analyzer prior to 10.5 | IIS


  • HTTP internal Server Error in Browser.
  • HTTP Error 500.21 - Internal Server Error. 
  • Handler "ExtensionlessUrlHandler-ISAPI-4.0_64bit" has a bad module "IsapiModule" in its module list.
  • Starting with version 10.5+, the GSX installer runs a prerequisite check highlighting missing IIS components. 

How to Solve the Issue

The HTTP 500.21 error is caused by a partial installation of IIS, specifically missing ISAPI modules. To fix the issue, we simply need to locate the IIS components and add these missing modules. A simple click to install the components and restart of the IIS server to load the changes will fix the problem.

Microsoft provides a procedure to install the IIS components for each Operating System: Install and Configure Internet Information Services for Dynamics NAV Web Client.

In case you are running Windows Server 2012 and you need to enable ISAPI modules, we also provide a dedicated article on how to install these missing components.

Adding components to the IIS server will require a restart once installation of the module is complete. You will find detailed instructions on restarting your IIS in this article.

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