Adding to Cache Object NOT WORKING!

I am trying to add an array list to a cache object in my WebService. But it only loads the first 2 attempts and ignores any other attempts to load data into the cache.

Why?

Code:

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Imports System.Web.Services
'Imports System.Web.Caching.Cache

<System.Web.Services.WebService(Namespace:="http://tempuri.org/wsTranscriptsTest/Service1")> _
Public Class HoldingTank
    Inherits System.Web.Services.WebService
    Dim strArray As New ArrayList

#Region " Web Services Designer Generated Code "

    Public Sub New()
        MyBase.New()

        'This call is required by the Web Services Designer.
        InitializeComponent()

        'Add your own initialization code after the InitializeComponent() call

    End Sub

    'Required by the Web Services Designer
    Private components As System.ComponentModel.IContainer

    'NOTE: The following procedure is required by the Web Services Designer
    'It can be modified using the Web Services Designer. 
    'Do not modify it using the code editor.
    <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()
        components = New System.ComponentModel.Container
    End Sub

    Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
        'CODEGEN: This procedure is required by the Web Services Designer
        'Do not modify it using the code editor.
        If disposing Then
            If Not (components Is Nothing) Then
                components.Dispose()
            End If
        End If
        MyBase.Dispose(disposing)
    End Sub

#End Region


    <WebMethod()> _
    Public Function HelloWorld() As ArrayList
        If Context.Cache("strArray") Is Nothing Then
            CreateCache()
        End If
        Dim arrReturnList As ArrayList = CType(Context.Cache("strArray"), ArrayList)
        Context.Cache.Remove("strArray")
        Return arrReturnList
    End Function

    <WebMethod()> _
  Public Sub FillCache(ByVal strValue As String)
        If Context.Cache("strArray") Is Nothing Then
            CreateCache()
        End If
        strArray.Add(strValue)
        Context.Cache.Add("strArray", strArray, Nothing, Now.AddHours(1), Nothing, Caching.CacheItemPriority.High, Nothing)
    End Sub

    Private Sub CreateCache()
        strArray.Add("StarterValue")
        'Context.Cache.Insert("strArray", strArray)
        Context.Cache.Add("strArray", strArray, Nothing, Now.AddHours(1), Nothing, Caching.CacheItemPriority.High, Nothing)
    End Sub
End Class


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