Iax2 trunk to unlimitel.ca failed with "No authority found" CAUSE CODE : 50

Hi guys,

I am having issue with unlimitel trunk connections. the out bound call is success. but failed with inbound call. After the trunk debug, I could see the error code as below,

CAUSE : No authority found
CAUSE CODE : 50

my configuration for inbound:

disallow=all
allow=ulaw
canreinvite=no
context=from-pstn
type=friend

Register String: MYDID:[email protected]

anybody could help or give some directions, much appreciated.

Thanks for any help.