Answer detect problem

Hi,

When I make calls with X-lite or other softphones, x-lite doesn’t detect that the phone is answered and hungup.
Here is our config:

sip.conf:

[general]
vmexten=*97
disallow=all
allow=ulaw
allow=alaw
allow=gsm
context=mycontext
callerid=Unknown
notifyringing=yes
notifyhold=yes
limitonpeers=yes
tos_sip=cs3
tos_audio=ef
tos_video=af41
nat=yes
canreinvite=no
externip=xx.xxx.xx.xxx
localnet=192.168.5.0/255.255.255.0

[2000]
type=friend
secret=1234
qualify=yes
port=5060
pickupgroup=
;nat=yes
mailbox=2000@device
host=dynamic
dtmfmode=rfc2833
dial=SIP/2000
context=mycontext
canreinvite=no
callgroup=
callerid=device <2000>
accountcode=
call-limit=50
disallow=all
allow=alaw
allow=ulaw
;allow=g729
allow=gsm

[myprovider]
disallow=all
port=5060
type=peer
context=mycontext
host=xx.xx.xx.xx
fromdomain=xx.xx.xx.xx
canreinvite=no
;nat=yes
;qualify=no
allow=ulaw
allow=alaw
;allow=g729
allow=gsm
;allow=all

Thanks in advance.