I transplanted it late last summer, into soil obtained at my nursery which I've used in all my plants, so I'm fairly sure it's draining fine. It has been a wet winter here, and my plants are somewhat protected from it, so I don't think it's root rot. I have started watering lately when we go several days without rain and the sun is out (low 70's), and it does seem to like a lot of water. Often on hot summer days I'll have to water it twice a day.
My lantana is a Lantana camara 'Landmark Rose Glow.' It has beautiful pink and yellow flowers.
I think now that I just have to be patient. Nature does things in her own time.