I raised 2 common snappers from babies once, and one ate anything and everything, while the other didn't seem to eat much at all for many months.
Small pieces of raw catfish, whiting, or pollock, live earthworms, live crickets, small pieces of cooked chicken should be offered. Most of the aquatic turtles I've raised didn't care for wardleys turtle sticks.. So, if you're using that, try reptomin. Turtles can't seem to resist that.
If none of that works, do like the other person mentioned, just give it time. It could be eating just a little bit, not enough to notice, for the first few months, but it should eventually come around.