My experience is I think once ticketed the airline and NCL don’t communicate.
Last fall I had booked my daughter and I on a cruise with the airfare.
Last minute My daughter could not make it so told them at the airport she was not coming, fully expecting the return to be cancelled, but it was not , I had to tell them at the airport on the day I returned.
At the port told them she was not coming’ but I don’t think they did anything, cabin attendant kept asking where she was all week and would get random messages from cruise staff asking how she was enjoying her 1st NCL cruise. Her latitude accounts showed she cruised and the personal cruise planners keep leaving messages about a special offer for her to book a second cruise. Never looked into a credit of the port fees as I used Credits from a 2020 cruise that were to expire .