I don't know if you're still around or not, but I'll reply anyway.
Your turtle may be so young that he/she is still living off of the nutrients provided by the yolk. It can sometimes take several weeks before a baby turtle begins to eat. Most take a few days at least.
Stinkpots are fairly secretive turtles, especially when young. Think about it, this tiny guy/gal is a snack for so many things in the water. They often need to feel secure in order to eat. Place a lot of structure in the tank...driftwood, water plants like anacharis, smooth rocks, even terra cotta pots broken in half and laid on their side. Anacharis is great...it's cheap from any pet store with aquariums, turtles can munch on it, and they love to hide amongst it. Just lay it in the shallow water. Make sure the water depth is enough to where the turtle can right itself if it is flipped over.
A heat emitting UV bulb is great when placed over a basking spot. It'll even warm the water, especially at that depth. Stinkpots don't need very warm water. The basking spot at one end of the tank will give the little thing the opportunity to warm up if it needs to. At around room temp.(70 to 75), no additional heat source would be required for a Stinkpot aside from the basking bulb. Temps can drop fairly low at night.
Offer only live items at this point...no need to foul the water with anything else. Earthworms, waxworms, mealworms, pinhead crickets, baby superworms, etc. are all great. Earthworms are probably your best bet. They'll wiggle around in the water long after most insects have drown. Leave the little guy/gal alone as much as possible...it's more likely to eat when it feels safe and secure. Live insects should be the staple diet with other things mixed in. Reptomin is often relished.
I hope the little turtle is still doing ok.