Admin change password

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ASP.NET4

I am try to enable admins a way to change passwords for when a user forgets their answer to the security question. But I can not get it to work. Username is login name. Here is my code:

Protected Sub btnResetPasswordClick(sender As Object, e As EventArgs)
       Dim userName As Label = Me.FormViewUserAccess.FindControl("UserNameLabel")
      
       Dim mp As MembershipProvider = Membership.Providers("AspNetAdminMembership")
       Dim user As MembershipUser = mp.GetUser(userName, False)
       Dim pass As String = user.ResetPassword
       Dim mm As New System.Net.Mail.MailMessage("mysite.com", user.Email)
       mm.Subject = "My Website"
       mm.Body = "Your password has been changed to: " & vbCrLf & pass & vbCrLf & _
           "Please login and change your password" & vbCrLf & _
            " SYSTEM GENERATED EMAIL - DO NOT RESPOND"

       Dim client As New SmtpClient
       Try
           client.Send(mm)
       Catch ex As Exception

       End Try
End Sub

Here is what I have in my webconfig:

<membership>
    <providers>
        <clear/>
        <add name="AspNetSqlMembershipProvider" type="System.Web.Security.SqlMembershipProvider" connectionStringName="ApplicationServices" enablePasswordRetrieval="false" enablePasswordReset="true" requiresQuestionAndAnswer="true" requiresUniqueEmail="false" maxInvalidPasswordAttempts="5" minRequiredPasswordLength="6" minRequiredNonalphanumericCharacters="0" passwordAttemptWindow="10" applicationName="/"/>
        <add name="AspNetAdminMembership" type="System.Web.Security.SqlMembershipProvider" connectionStringName="ApplicationServices" enablePasswordRetrieval="false" enablePasswordReset="true" requiresQuestionAndAnswer="false" requiresUniqueEmail="false" maxInvalidPasswordAttempts="5" minRequiredPasswordLength="6" minRequiredNonalphanumericCharacters="0" passwordAttemptWindow="10" applicationName="/"/>
    </providers>
</membership>

Can someone point out where I am going wrong, I am new to asp.net and I get the following error: The provider user key supplied is invalid. It must be of type System.Guid.
Parameter name: providerUserKey