I've been on many cruises, including NCL ones, that have missed planned ports of call once underway and the normal procedure for the ship to refund that particular port's fees and taxes is generally done as an instant form of credit to each passenger's individual on board account. Often, unless a United States, Canadian, or major European tourism ports, the fees and taxes rarely exceed $35 per passenger for many ports and the account credit can easily be missed on the final printout of on board expenses.
Only when a planned port is cancelled prior to the ship's departure, but after final payment is tendered, the port fees and taxes will be refunded to the original form of payment. This can take as long as 1-3 billing cycles of the credit card to show back on the account after the port cancelation, is confirmed, but there are exceptions that can take longer. Prepaid cards often don't allow for refunds if the card backing has been exhausted and it can take the accounting department from the cruise line's main office anywhere from 2 months to a year of back and forth with the prepaid card issuer to straighten out the facts before the cruise line will cut a check to the person named on the card or primary passenger that made the booking. Another exception is if you booked through a 3rd party be it a travel agent, booking consolidator, or open group travel coordinator. Because of the way these 3rd party booking contracts are written the preboarding cruise line refund goes to that company or individual and it is upon them to forward that funds to their direct customers in whatever way their direct to consumer contract indicates.
The bulk of your port fees and taxes, commonly 60-80%, goes to your embarkation and debarkation ports, so it is not an even distribution to all ports. Though certain style expedition cruises can have a large portion of their fees and taxes as permits just to traverse certain waters like going through the locks at a canal (tolls fees) or entering certain areas like the Antarctic (because of liability riders).
Since forming a class action suit against any maritime entity requires the filer to have a licensed legal professional of the country the ship is flagged in initiate the filing, it can be more costly in legal fees to attempt to make what could be an unsuccessful suit, for a small amount of recovery. My advice would be to first request an emailed version of your final on board account for the entire group/family on your booking and booking payment summary to verify that no credit was applied or if another form of refund was issued it went to the wrong passenger's card or address. Next I would revisit any and all social media and community forum pages specific to the cruise date or at the very least for that ship (Meta has groups for everything now) to gauge how many other passengers had or are having the same experience as you, before proceeding as a group to a legal advisor.
