Well male emeralds don't usually become sexually mature until they reach 4-5 years. They also aren't usually sexually active when spring pops around. Breeding season is generally late October through mid Feb and you usually have to "cycle" them to get them in the mood. How are your DTH temps and humidity, as well as your NTL's? Are you turning all heat sources off when you attempt feeding?
Emeralds are excellent at hiding symptoms of problems. Have you noticed any strange breathing noises or liquid from the nostrils or mouth? Does he go into hunting mode at night or stay coiled?
Craig