Any tips on setting this up on a 6x server? I just have the NANPA dialing plan enabled but the system doesn't dial out when I enter 9 011 44 844 415 6790. Appreciate any input, thanks.

In your Services area of the External Dialing Rules, what does it say under Service Group? It should correlate with the type of outside lines or circuits that you have (C.O. lines, SIP proxies etc). There is a drop down for those choices.