Update software function doesn't work if software is already open - vb.net

Question

I've a function that check update for my application. I've two mode for execute this function, in the first time that the application's start and in the tooltip menu. If I execute the software for the first time all working good, the update is found , but if I press on my button in the tooltip menu the same function (the exact function) not working. In particular the update is found but the software for download it (infinity blue) doesn't start.
This is the function:
Dim MyAppName As String = "Sund.exe"
Dim url As String = "www.site.com/update/" & "FileUpdates371.php"
Dim pageRequest As HttpWebRequest = CType(WebRequest.Create(url), HttpWebRequest)
Dim pageResponse As WebResponse = pageRequest.GetResponse()
Dim filelist As String : Dim Mainlist As String
Using r As New StreamReader(pageResponse.GetResponseStream())
filelist = r.ReadToEnd
If Not IO.File.Exists(Application.StartupPath & "\" & "Updates") Then
IO.File.WriteAllText(Application.StartupPath & "\" & "Updates", filelist)
End If
Dim sr As New StreamReader(Application.StartupPath & "\" & "Updates")
Mainlist = sr.ReadToEnd
Dim FileLines() As String = filelist.Split(New String() {Environment.NewLine}, StringSplitOptions.RemoveEmptyEntries)
Dim MainLines() As String = Mainlist.Split(New String() {Environment.NewLine}, StringSplitOptions.RemoveEmptyEntries)
If Not Mainlist = filelist And Not FileLines.Length < MainLines.Length Then
Dim answer As DialogResult
answer = MessageBox.Show("Update available", "Update", MessageBoxButtons.YesNo, MessageBoxIcon.Question)
If answer = vbYes Then
Dim App As New Process
App.StartInfo.FileName = Application.StartupPath & "\" & "InfinityBlue.exe"
App.StartInfo.Arguments = "Update|" & MyAppName & "|" & url
App.Start()
Me.Close()
End If
End If
End Using
If My.Computer.FileSystem.FileExists(Application.StartupPath & "\" & "InfinityBlueUpdate.exe") Then
My.Computer.FileSystem.DeleteFile(Application.StartupPath & "\" & "InfinityBlue.exe", FileIO.UIOption.OnlyErrorDialogs, FileIO.RecycleOption.DeletePermanently)
My.Computer.FileSystem.RenameFile(Application.StartupPath & "\" & "InfinityBlueUpdate.exe", "InfinityBlue.exe")
End If
I've also tried to catch the exception and there isn't exception. Why happean this?