Can't connect to fwd after IP address change

recently changed IP address of AAH box.
everything is working apart from fwd (free world dial up) had been working previously but now is showing as unreachable.

have checked iax.conf and this is showing correct ip
can ping from aah server and can use iax remote phone to connect from outside.

also send voicemail mails with no problem

this is running on internal network that goes through multi homed server then router…

any ideas