Something that may help is to change the nectar more often. In our TN heat, 3 days is the absolute maximum for the nectar, 2 days would be better.

I agree with ctnchpr about changing the nectar more frequently. You mentioned other feeders--were they of a different style and did the hummingbirds use them? As odd as it may seem, hummingbirds can have strong preferences for particular feeder designs. It isn't so much bowl vs. jar, but the angle of the feeder ports, color and shape of the flowers, distance to the perch (if available) and other unknown and mysterious considerations. There may be regional preferences--I am not sure. But I do know, when someone gave me a fancy Avant Garden Looking Glass feeder as a gift, the hummingbirds fed from it only a small fraction as often as my plastic bowl feeder, even though they were hung next to each other. And when I removed their favorite feeder to clean it, they would wait rather than use the other style.