Hi @Penyo ,
IIS is different from IIS Express in Visual Studio. When you try to visit site on IIS and let it run .exe file, it is actually the application pool that starts and runs the .exe file. So you need to make sure that application pool identity has full control permission to .exe file.
The easiest way is setting application pool identity to administrator. If you worry about security issue, go to directory(which store .exe file) properties, in Security tab add the IIS AppPool\app pool name
and set it full control permission.
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Best regards,
Bruce Zhang