No audio from Festival using IP phone

I don’t receive any audio from Festival on a Polycom IP phone.
Festival does work fine when using softphones or zap extensions, just not thru a Polycom IP 601 phone. The logs show normal execution without any errors.

Here is my SIP configuration, any ideas?

;Polycom IP 601 phone, SIP.LD version: 1.6.2.0041, bootrom version: 3.1.0.0269.
[ext04]
type=friend
username=ext04
secret=xxxx
nat=no
host=dynamic
dtmfmode=rfc2833
defaultip=192.168.0.13
disallow=all
allow=ulaw
allow=g729
progressinband=no
context=default

Check out my “reply”: forums.digium.com/viewtopic.php?t=5781