Is this a new set up? Yes
Did it work before? New set up
Do other calls work? Inbound and outbound calls are working fine within the UK. The sip trunk provider is +44 and set up accordingly. They did inform to set it up as e164 but not sure how to do that.
Have you enabled the country in the allowed list from the management console? Yes
Have you made the correct outbound rule? Not sure
Have you looked in the activity log to see why? I saw that it terminates and cause is BYE from PBX
Does your provider allow you to dial internationally? Yes