1) You bought this as a condo unit and the certificate of occupancy Apartment?
2) Were the other "attached" units bought and sold as condos?
If so then you or the seller can go to local B&S and request a change of occupancy, it should not cost anything it must have been an oversight, or there was never a final inspection on that particular unit.
It should not be any problem if the other units were changed.
If you need our services in any manner we can help you.