My painted isn't RES but he's similar to one.
From day one I fed him a huge variety of foods, from cut up whole fish, to pinhead crickets, a variety of live worms and some pellet food.
My painted was CB & a tiny hatchling when I got him, he took a few days to get used to a new home but in the beginning I spent a lot of time looking at him through the glass so that he'd get used to my face & not be afraid of me.
Try that.. make him get used to seeing you, then try a lot of different foods, he should want to eat soon.
Since you say there is a lid on top of the tank try knocking on it & speaking before you take that lid off.
If they have a warning ahead of time that the lid is about to come off they'll learn to not fear it.
I have 2 tarantulas in 2 different containers, to feed them I have to take the lids off. They used to totally freak out when I did that. I started knocking on the lid before I'd take it off & once I started doing that, they stopped freaking out. I figure if a freakin' spider can learn that, a more intelligent turtle most certainly can learn it.
One other thought.. what's the water temperature? If it's too cool he won't eat. It should be 78-80 or so.
If he really isn't eating & the water temperature is high enough, I'd consider a check up with a vet to make sure he's ok.
Any turtle could have a parasite problem & not eating would be a symptom of that.
Good luck with him... or her. 
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PHRatz