we where testing IAD2432 with SIP and it seems we can not make it to support hook-flash functionality. When I dial first number and press flash button I get a second dial tone and first phone conversation is on hold, after dialing a second number when I press flash button I get a third dial tone not a 3-way add hock conference as with traditional PBX like feature and first call gets dropped.
Bellow is the documentation I used to configure those features with SIP:
Any suggestion on making this working will be welcome. Thank you in advance.
The config is attached.