Ever since the FHL in Salt Lake stopped charging for photoduplications, demand has increased and service slowed. However, these might be some other reasons requests are not fulfilled. #1, you must provide the film title and exact roll number; #2, the index may have errors (they can be hard to read!). If you can identify the film number, you can always order it and search yourself.
Be patient, these folks are all volunteers and perform a valuable FREE service to all of us. On the other hand, the city of New York costs $$$ and, in my experience, sometimes fall short.