Lantana leaves are curling up from the sides.
Lantana plants the leaves are curling up from the sides and the flowers stems are drooping.
Certified GKH Gardening Expert
Without a photo and detailed information it would be hard to say for sure. I can only take guesses at this point. My best guess would be overwatering. Please include detailed information on its care and photos. This will help me to see what is going on.
In the meantime, this article will give you a good idea of their care requirements: https://www.gardeningknowhow.com/ornamental/flowers/lantana/lantana-plants.htm