PasswordStrength not showing

Hi All,

I cannot understand why my PasswordStrength control is not showing.

Here is my code:

<asp:TextBox runat="server" ID="Password" TextMode="Password" CssClass="txtbox" /><br />  <br /><asp:PasswordStrength ID="PasswordStrength" 
         runat="server" 
         DisplayPosition="RightSide"
         TargetControlID="Password" 
          RequiresUpperAndLowerCaseCharacters="false"
            StrengthIndicatorType="BarIndicator" 
         TextStrengthDescriptions="Not enough long; Not enough long; Fair; Strong; Very Strong" 
         HelpStatusLabelID="passwordstatus" 
         PreferredPasswordLength="8" 
         MinimumSymbolCharacters="1"
        MinimumUpperCaseCharacters="1" 
         MinimumNumericCharacters="1"
         BarBorderCssClass="barBorder" 
          StrengthStyles="Notenoughlong;Fair;Strong;VeryStrong;"></asp:PasswordStrength> <br /> <asp:Label ID="passwordstatus" runat="server" Text="Label"></asp:Label>

here is my CSS:

.BarBorder
{
    border: 1px solid #CCCCCC;
    width: 233px;
    padding: 5px;
    float: left;
}
.Notenoughlong
{
    background-color: #C60000;
}
.Fair
{
    background-color: #4FB000;
}
.Strong
{
 background-color: #4FB000;
}
.VeryStrong
{
 background-color: #4FB000;
}

What am I missing? 

I didn't add the Scriptmanager in the register page because this has been added already into the masterpage.

Thanks