Is litter training young female rats a waste?

Most rats are easily trained, but some never get it. Like dogs, some are just faster learners than others. How long have you been trying this? It could take a while for them to catch on. Make sure their entire cage is cleaned thoroughly (change sheets and wipe down). Make sure none of their scent is anywhere other than their litter box. It can take a couple months before they catch on, but just be persistent. :) Hope it works out.