OnComm event does not trigger

Question

I'm trying to get the input of a 3g modem when it receives sms.

This is the code I'm using to trap any incoming sms.

Private Sub MSComm1_OnComm()
   Select Case MSComm1.CommEvent
      Case comEvReceive
         Do While MSComm1.InBufferCount > 0
            strInput = strInput & MSComm1.Input
         Loop

         Sheets("Sheet1").Range("A1").Text = strInput
   End Select
End Sub

Regardless the code, the event does not fire as if nothing is received.

What do I miss here?

Thank u.