Fiddler Classic app not launching after installation

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Fiddler Classic Windows
arun
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arun asked on 29 Apr 2023, 07:41 AM

During the installation of the app I get this screen saying Unhandled Exception:System.IO.FileNotFoundException:Could not load the file or assembly system.core. I also got another error saying "Please add Fiddler classic installion directory to path environment variable". I have included the image. But the app is installed and after that when I try to launch it is not running.  Nothing happens when I run the app.

I am using windows 11 and have Dot net framework 3.5 and and 4.8 installed. Their features are turned on. I tried moving the system.core file from dot net framework to where fiddler is installed, it didn't work.

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Nick Iliev
Telerik team
answered on 02 May 2023, 06:14 AM

Hello Arun,

 

The error indicates that, for some reason, Fiddler Classic lacks the rights to install or access some of the NET files properly. The same issue was discussed a while ago in this forum thread, and the user determined that third-party security tooling caused the problem. Please check and ensure that no antivirus, security tool, or security policy is striping the Fiddler Classic application of administrative rights.

 

Regards,
Nick Iliev
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arun
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commented on 03 May 2023, 01:22 PM

Thank you for the help. I can run the app now. I don't have 3rd party security apps. I ran sfc scannow and updated windows. I don't know which one fixed it.
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Fiddler Classic Windows
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Nick Iliev
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