C# try catch not working on some machines

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C#

I have a try catch around some code that gets a response from a web request. The following is the code

var token = "";
try
  {
    var response = req.GetResponse();
    using (var sReader = new streamReader(response.GetResponseStream()))
    {  
       token = sReader.ReadToEnd();
     }
catch (webException we)
{
   token = "ERROR: " + we;
}
catch (Exception e)
{
   Token = "ERROR: " + e;
}

This line -

var response = req.GetResponse();

is the one that fails. The fact it fails is a different issue that I'm working on with a different group.

The problem is the catch statement only catches the error on 2 of the 3 test machines. The third one it doesn't catch and I get a unhandled exception error.

What I have tried:

Somewhere I read that the issue could be a mismatch .NET version, so I've made sure the app targets .NET 4.6 and all 3 machines have 4.6 or greater installed.

Machine 1 - Windows 10, .NET 4.6.2 - catch block works
Machine 2 - Server 2008, .NET 4.6 - catch block works
Machine 3 - Server 2008, .NET 4.6 - catch block does not work.

What else can I look at?