Esta é uma versão melhorada da resposta da  tbone  que funciona nas versões alemãs. 
Private Declare PtrSafe Function FindWindowA Lib "user32" (ByVal lpClassName As String, ByVal lpWindowName As String) As Long
Private Declare PtrSafe Function SetWindowPos Lib "user32" (ByVal hwnd As Long, ByVal hWndInsertAfter As Long, ByVal X As Long, ByVal Y As Long, ByVal cx As Long, ByVal cy As Long, ByVal wFlags As Long) As Long
Private Declare PtrSafe Function BringWindowToTop Lib "user32" (ByVal hwnd As Long) As Boolean
Private Declare PtrSafe Function SetForegroundWindow Lib "user32" (ByVal hwnd As Long) As Boolean
Private Declare PtrSafe Function SetFocus Lib "user32" (ByVal hwnd As Long) As Long
Private Const SWP_NOSIZE = &H1
Private Const SWP_NOMOVE = &H2
Private Const FLAGS As Long = SWP_NOMOVE Or SWP_NOSIZE
Private Const HWND_TOPMOST = -1
Private Sub Application_Reminder(ByVal Item As Object)
    Dim ReminderWindowHWnd As Variant
    On Error GoTo err
    'Loop 25 times as FindWindowA needs exact title which varies according to number of reminder items...
    Dim iReminderCount As Integer
    For iReminderCount = 1 To 25
        'Try two syntaxes...
        ReminderWindowHWnd = FindWindowA(vbNullString, iReminderCount & " Erinnerung")
        SetWindowPos ReminderWindowHWnd, HWND_TOPMOST, 0, 0, 0, 0, FLAGS
        BringWindowToTop (ReminderWindowHWnd)
        SetForegroundWindow ReminderWindowHWnd
        SetFocus ReminderWindowHWnd
        ReminderWindowHWnd = FindWindowA(vbNullString, iReminderCount & " Erinnerung(en)")
        SetWindowPos ReminderWindowHWnd, HWND_TOPMOST, 0, 0, 0, 0, FLAGS
        BringWindowToTop ReminderWindowHWnd
        SetForegroundWindow ReminderWindowHWnd
        SetFocus ReminderWindowHWnd
    Next
Exit Sub
err:
    Debug.Print err.Number & " - " & err.Description & " (iReminderCount = " & iReminderCount & ")"
    Resume Next
End Sub
Adicionei títulos de janelas alemãs e também algumas novas funções  BringWindowToTop ,  SetForegroundWindow  e  SetFocus )). 
Funciona no meu Windows 10 alemão juntamente com o Outlook 2016. 
Consegui não gerar um novo certificado (premir Start e introduzir “certificado” não revelou nada), mas simplesmente seleccionei outro certificado na lista ao assinar.