ISDN setup in call forwarding

[SYSUSER2015]

Please I have avaya aura 6.0

I have configure a mobility " when a user is not available, call is forwarded to his mobile".

I have a problem: when a call is coming from external and forwarded to mobile, The call is forwarded but it is in one way and I can't her the caller.

Note that I have an ISDN link from provider.

my question is: when a call come to user and there is no answer, how the ISDN will setup again and initiate a call: like establish a normal call from user.

is there any parmeters to change.

note that when a call come to user from internal user, in case of no answer the call is forwarded to mobile without any problem.

Thank you

 

[Rubzrain]

Can you provide your configuration. And also do a list trace.