We overwintered our Stevia plant in our greenhouse a year ago, but this winter we divided the plants, repotted them and kept them in the greenhouse, but so far there isn't a hint of anything coming up.
Your plant is Piqueria trinervia, known for its profuse winter blooms. Stevia is easily propagated by seeds, cuttings, or division. It's native to Mexico and Chile, so will appreciate living in your greenhouse. Give your divisions a little more time to sprout before you give up on them.