Additional info: He's really a smart boy; he's not lazy and not stubborn. Lunging initially took longer than I expected for him to catch on but was going well ... then life and a rainy spring got in the way for a couple of weeks. He's always been much better counter-clockwise but now simply will not pick up the trot when lunging clockwise. Physically, he's just fine. He'll do it without a problem under saddle (tested briefly several times to just make sure). When I ask, he may go 1/2 a lap (sometimes not even) then stops, turns into face me (doesn’t come in though) and looks at me. Eventually, I can get him to walk off again, but it sometimes takes quite a bit of effort. He is unaffected by the lunge whip. We don't have a round pen right now (panels have been borrowed while parts of center are under constructions). He trots fine other direction and is starting to learn to pick up the canter. He's not lazy - if I take him off the line and crack the whip in the arena - he'll run around the whole time. I've tried everything I can think of, we've started all over again, I've tried a tight circle and a large circle, I've tried running and being very energetic, tried even popping him with the whip. I cue him with a cluck, then, if he's not trotting, a sharp TR-OT, and then, if he's still not trotting, a whip pop in the air (waist level) behind him. I've verified my angle to him and the whip are correct. Please help -I'm incredibly frustrated.