Custom Ribbon doesn't refresh

First of all many thanks for take some time to read my question.

I'm new with XML-VBA (actually is my 1st incursion on this)

I've create the following custom ribbon for an Excell addin:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<customUI onLoad="RibbonOnLoad" xmlns="http://schemas.microsoft.com/office/2009/07/customui">
 <ribbon> 
<tabs>

<!-- Creamos tab para el administrador con sus botones-->

<tab id="customTab" label="BPR Moldeo" insertAfterMso="TabView">

<!-- Creamos grupo de botones 2 "Acceso"-->
				
				<group id="customGroup2" label="Activar sistema" tag="Accede">
					<button id="customButton12" label="Log in" size="large" onAction="sesion" imageMso="ReviewProtectWorkbook" />
					

</group>


<!--Group 0 "Generar BPR"-->
				
				<group id="customGroup0" label="BPRs Moldeo" getVisible="GetVisible" tag="LGGenerar">
					<button id="customButton0" label="Generar" size="large" onAction="Inicio" imageMso="PivotTableInsert" />
					

</group>



<!-- Group Note-->

				<group id="customGroup1" label="By I. Q. Leonel Garcia [QA AL]" getVisible="GetVisible" tag="LGAyuda">
					<button id="customButton11" label="Dudas / Comentarios" size="large" onAction="Envia_Mail" imageMso="FileSendMenu" />
				
				</group>

<!-- Group Exit-->

				<group id="customGroup3" label="Desconexión" getVisible="GetVisible" tag="LGSalir">
					<button id="customButton13" label="Salir" size="large" onAction="Oculta" imageMso="WindowClose" />
				
				</group>

			</tab>
		</tabs>
	</ribbon>
</customUI>

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And the following code in my VBA project (not developed for me, as I mentioned I'm new on this)

Module Ribbon

Option Explicit

Public Rib As IRibbonUI
Public MyTag As String

'Callback for customUI.onLoad
Public Sub RibbonOnLoad(ribbon As IRibbonUI)
    Set Rib = ribbon
End Sub

Sub GetVisible(control As IRibbonControl, ByRef visible)
    If MyTag = "show" Then
        visible = True
    Else
        If control.Tag Like MyTag Then
            visible = True
        Else
            visible = False
        End If
    End If
End Sub

Sub RefreshRibbon(Tag As String)
    MyTag = Tag
    'If Rib Is Nothing Then
    '    MsgBox "Error, reinicia Excel"
    'Else
        Rib.Invalidate
    'End If
End Sub

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Module Buttons

Sub ShowAllButtons()
'Show All
    Call RefreshRibbon(Tag:="*")
End Sub

Sub HideButtons()
'Hide all with a Tag that start with "LG"
    Call RefreshRibbon(Tag:="Login")
End Sub

Sub Oculta(control As IRibbonControl)
Call HideButtons
End Sub

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All works fine when I start Excel, the addin is loaded, the custom "test Tab" is showed, once the login is completed three additional buttons are showed, my problem is that after I press button "Generar"  or  "Dudas/comentarios" the macro assigned to these run  OK and when I press the "Salir" button to hide the buttons but I received the notification that something went wrong (Runtime error 91: Object variable or with block variable not set), I've reviewed and looking for information but I have not find nothing related.

Many thanks in advance for your help.