Cannot get Excel event to fire on Workbook Open

When opening an excel document through the EPM Add-in via the web client, I cannot get the the Workbook_Open() procedure within ThisWorkbook to fire. It works fine (i.e. fires as it should) if I just double click on the excel file and open the file that way. I am trying to get the code below to fire but do not worry so much about what this code is doing but the fact that it does not even fire

Private Sub Workbook_Open()

    Dim EPMObj As New FPMXLClient.EPMAddInAutomation
   
    EPMObj.Logon

    Run (“UnprotectLayout.UnprotectLayout”)

    ‘This code is used to “trip” the parameter values to be set to the sunset colors
    ‘so that a refresh is indicated when the conditional formatting triggers for the
    ‘selection boxes F3, 5 and 7
    Cells(3, 12).Value = Cells(3, 12).Value & “TripTheColor”
    Cells(5, 12).Value = Cells(5, 12).Value & “TripTheColor”
    Cells(7, 12).Value = Cells(7, 12).Value & “TripTheColor”
   
    Run (“ProtectLayout.ProtectLayout”)

   
End Sub