Hmm, well, you do not have an obvious case of black tip. But the picture was taken in shade so, I hope it is getting 6 hours of direct sunlight. I do not see any indications of winter damage due to cold temperatures on the picture's side of the trunk. Can you confirm that the trunk firm or does it feel soft? Check near the base and some inches below the tip. If it is soft, it may be starting to rot. Otherwise, you can wait a bit more to see if it takes off if put in more sun. Another test: poke a needle into the branch to see if latex oozes out. If no latex, it may be rotting. Of course, in the middle of the summer, many plants do not want to leaf out and go semi-dormant until temperatures recede. During this inhospitable time, you can temporarily change the pot's location so it still gets sunlight (morning only) but not much during the hottest part of the afternoon-evening day.
But try more sunlight. In Spring, they normally need a certain amount of warm days and nights to stop their dormancy and begin actively leafing out. Maybe it is not getting enough in its current location.
Standard things to look for this time of the year... Make sure there are no pests around (spider mites, whiteflies, aphids, thrips, scale, mealybugs); that the potting mix drains very well and that the pot's drainage holes also drain well. How much water do you give the pot (in gallons) and how often? Since there are no leaves losing internal moisture, the plant should not need as much water as the one that successfully leafed out. What fertilizer do you use and how often?
