I'm the guy who asked the same question a few days ago that phonemeister was talking about.
My problem was similar, but not exactly the same. My VM system was answering, but it was answering as if you had just called the VM pilot number. Configuring the forward digits fixed that(I tried it both ways, with the trailing 1 and without and it worked both times).
From what you are describing, it sounds like it is either not passing the forwarded digits, or the VM is not understanding what it is hearing.
Can you log into the voice mail by calling the regular voicemail pilot number? That would determine if your DTMF tones are being sent and heard correctly.
