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Callisto Help > Setup and user administration > A note on error 500 Messages

A note on error 500 Messages

Error 500.19

When Callisto is installed on a server which also hosts WSUS, there is a bug in the  XPress compression schema module (suscomp.dll) installed with WSUS. The 64bit version of suscomp.dll will try to load into the 32bit Callisto AppPool, which causes the AppPool to crash.

So, if you have WSUS installed on the Callisto server, or you see the following error when you try to browse to the Callisto website:

HTTP Error 500.19 – Internal Server Error
Module StaticCompressionModule or DynamicCompressionModule

In an elevated command line, run the following:

%windir%\system32\inetsrv\appcmd.exe set config -section:system.webServer/httpCompression /-[name='xpress']

This should fix the problem and it has no impact on ConfigMgr or WSUS functionality.

It is also possible that 32-bit support is disabled by default for the AppPool, in which case in the Advanced Settings for the Callisto App Pool in IIS Admin, check the following setting:

A further less common problem is that the web.config file is corrupt, this occasionally occurs during upgrade and results in some duplicate rows being added to the file which errors as shown here:

This error is caused by this section having errors in it, but there is normally further issues with the web.config file. There is a valid web.config file here which you can use to overwrite your faulty file, or contact us for assistance.

      <remove fileExtension=".woff2"/>
      <remove fileExtension=".woff2"/>
      <mimeMap fileExtension=".woff2" mimeType="application/font-woff2"/>
      <mimeMap fileExtension=".woff2" mimeType="application/font-woff2"/>

Error 500.0

We've had a few reports of customers with a generic 500.0 error immediately after installing Callisto. The main causes of this are:

DotNet 4.8 is not installed. The solution is to download DotNet 4.8 from here

Another reason for this error we hear is that DotNet 4.8 is pending a reboot. Callisto won't work until this has been completed.

If you've upgraded and immediately get a 500 error and none of the above are valid, there's a chance that the upgrade has not successfully removed the old Callisto installation. The quickest and easiest fix is to uninstall Callisto from the Add/Remove Programs interface, you might have two entries, uninstall them both. Then reinstall the latest version. All of your settings and configuration will be retained in the Callisto database.