Panasonic PBX 1 extention can't get outside calls by pressing "9"

[Nadeeshan]

Hii
We are using Panasonic KX-TEA308 PBX system with KX-T7730 masterphone.All extensions are working fine.But the problem is
1 extension (ext num 18-(jack 08)) phone can't get (dial) outside calls directly by pressing "9".It's giving line busy tone.but inside the intercome all phones can comunicate each other.
so do I have to re programme that extension ?if so plzz guide me to how to do that.(I'm not da person who programmed this before)
jack & extension numbers are programmed like

jack 2 - ext num 12
jack 3 - ext num 13....
like so

plzz someone help me to solve this peoblem
thanks all of u..

 

[obtsystems]

check co out day/night for that jack, may have no lines asigned for out going calls prog 405/406/407 day/night/lunch