C# Code generator with vowels and consonants vowels not showing up

I have a random key generator in C# that's supposed to generate a key in the following format:

consonant + vowel + consonant + vowel + four numerical digits

So for example it would be BABA1234 or ZUZU9876.

Currently, however, the vowels don't show up, though everything else does, so I end up getting output like B_B_1234, for example, where the underscores represent either spaces or unrecognized character boxes.

I've been looking through some examples such as this, this and this, but I still haven't gotten it to work. The C# code is as follows:

public static string shortText()
{
   string randomNumber = new Random().Next(1000, 9999).ToString();
   char c1 = consonant();
   char c2 = vowel();
   System.Threading.Thread.Sleep(400);
   char c3 = consonant();
   char c4 = vowel();

   return string.Format("{0}{1}{2}{3}{4}", c1, c2, c3, c4, randomNumber);
}

private static char vowel()
{
   int selected = new Random().Next(0, 4);
   List<int> list = new List<int> { 65, 69, 73, 79, 85 };

   return Strings.Chr(selected);
}

private static char consonant()
{
   int selected = new Random().Next(65, 90);
   List<int> list = new List<int> { 65, 69, 73, 79, 85 };

   if (list.Contains(selected) == false)
   {
       return Strings.Chr(selected);
   }
   else {
       return Strings.Chr(selected + 1);
   }
}

An additional note is that this code was originally written in VB (which is why there is a Strings.Chr in the C# code above, I added a reference to the VB library), where it worked correctly and generated codes according to the format in the beginning. I converted it over to C# and edited it slightly to remove the errors, but it looks like the conversion hasn't been perfect. Here is the VB code:

Public Class Form1
    Private Sub btnGenerateKey_Click(sender As Object, e As EventArgs) Handles btnGenerateKey.Click
        txtKey.Text = shortText()
    End Sub

    Private Shared Function shortText() As String
        Dim randomNumber As String = New Random().Next(1000, 9999).ToString
        Dim c1 As Char = consonant()
        Dim c2 As Char = vowel()
        System.Threading.Thread.Sleep(400)
        Dim c3 As Char = consonant()
        Dim c4 As Char = vowel()

        Return String.Format("{0}{1}{2}{3}{4}", c1, c2, c3, c4, randomNumber)
    End Function

    Private Shared Function vowel() As Char
        Dim list As List(Of Integer) = New List(Of Integer)({65, 69, 73, 79, 85})

        Return Chr(list(New Random().Next(0, 4)))
    End Function

    Private Shared Function consonant() As Char
        Dim selected As Integer = New Random().Next(65, 90)
        Dim list As List(Of Integer) = New List(Of Integer)({65, 69, 73, 79, 85})

        If list.Contains(selected) = False Then
            Return Chr(selected)
        Else
            Return Chr(selected + 1)
        End If
    End Function
End Class

Any help is much appreciated.