Missing a port in the harbour with max rank town and shipping?

Hi there,

I am wondering if I am missing something or there is a bug with my game? So I have both my town and shipping at max rank. However, I cannot seem to ship to a 6th location, I have available to me: Pondium, Riben Fell, Kalguur, Ngakanu and Te Onui. https://imgur.com/a/15xDZKz I have tried to attach an image, unsure if it will work >.<

Thanks
:)