Transcode from DTMF audio to RFC2833 telephone-event

I have installed a  Transcoding NIU in NN4500 ,and the image file is nnscx637m1p2.tar .I configured "RFC2833-mode  preferred" ,"RFC2833-payload   97" in session agent (sip server)  which support RFC2833 .

Then i made a test call ,from the trace result :RFC2833 (payload 97 which doesn't exist in ingress "INVITE")is added in sdp when SBC route the "INVITE" to the session agent(sip server).and the forwarded  signaling messages the just go as document described .

however , when there comes to the media  flow , the NN4500 doesn't transcode my in-band audio DTMF to RFC2833 telephone event.

and i download the  log.xserv in which there are some errors . hope the attachment can help .