Give it another day or so then worry a bit. Its not good to starve them but I had a stubborn kel that literally ate nothing for a couple weeks and was skin and bones. One day bam, it just clicked. Get some dithers too, the other fish eating will get it him going. The only reason I starved the fish is because I had 3 others that were eating just fine.
I used frozen brine shrimp. Broke a small piece off and put it in a plastic cup with some water from the tank. Let it thaw (5 min) swirl it around and dump it in. Mine went crazy for it.