Very nice buck. And look at that cover. You could walk 15 yds past him and you would never see him if he held tight. About the only way that you will get him is persistance and possibly agressive moves. Its getting late in the season. Try still hunting his bedroom. Moving slowly, very slowly. 100 yds in 1/2 hour. Take a step, look around, take another step, look around. Be sure the wind is in your face.
Or you can try grunting him in. One or two short grunts every 15 mins to 1/2 hour and use ample amounts of buck urine.
Obviously your trees stand location isn't his primary stomping grounds.