None of these worked for me. In the end I reverted to dotNet code which worked first time.

class Script
{
    static public void Main(string[] args)
    {
                if (args.Length < 3 || args.Contains("/?"))
                {
                    MainHelp(args);
                    return;
                }
       string _infile = args[0],
                        _outfile = args[2];
                string _password = args[1], _outpassword = (args.Length > 3) ? args[3] : "";
                Console.WriteLine(String.Format("{0} -> {1} with ({2} -> {3})", _infile, _outfile, _password, _outpassword));
                System.Security.Cryptography.X509Certificates.X509Certificate2 cert = null;
                Console.WriteLine(String.Format("Load {0} with {2}", _infile, _outfile, _password, _outpassword));
                cert = new System.Security.Cryptography.X509Certificates.X509Certificate2(_infile, _password, X509KeyStorageFlags.Exportable);
                Console.WriteLine(String.Format("Export {1} with {3}", _infile, _outfile, _password, _outpassword));
                System.IO.File.WriteAllBytes(_outfile, cert.Export(System.Security.Cryptography.X509Certificates.X509ContentType.Pfx, _outpassword));
                Console.WriteLine(String.Format("Export complete", _infile, _outfile, _password, _outpassword));
    }
    
     static public void MainHelp(string[] args)
    {
            Console.WriteLine("Usage pfxremovepwd [inpfx] [inpwd] [outpfx] [optional outpwd]");
            return;
    }
}

None of these worked for me. In the end I reverted to dotNet code which worked first time.

class Script
{
    static public void Main(string[] args)
    {
                if (args.Length < 3 || args.Contains("/?"))
                {
                    MainHelp(args);
                    return;
                }
       string _infile = args[0],
                        _outfile = args[2];
                string _password = args[1], _outpassword = (args.Length > 3) ? args[3] : "";
                Console.WriteLine(String.Format("{0} -> {1} with ({2} -> {3})", _infile, _outfile, _password, _outpassword));
                System.Security.Cryptography.X509Certificates.X509Certificate2 cert = null;
                Console.WriteLine(String.Format("Load {0} with {2}", _infile, _outfile, _password, _outpassword));
                cert = new System.Security.Cryptography.X509Certificates.X509Certificate2(_infile, _password, System.Security.Cryptography.X509Certificates.X509KeyStorageFlags.Exportable);
                Console.WriteLine(String.Format("Export {1} with {3}", _infile, _outfile, _password, _outpassword));
                System.IO.File.WriteAllBytes(_outfile, cert.Export(System.Security.Cryptography.X509Certificates.X509ContentType.Pfx, _outpassword));
                Console.WriteLine(String.Format("Export complete", _infile, _outfile, _password, _outpassword));
    }
    
     static public void MainHelp(string[] args)
    {
            Console.WriteLine("Usage pfxremovepwd [inpfx] [inpwd] [outpfx] [optional outpwd]");
            return;
    }
}