Same thing happened with stevia, dill and chives last year. I tried to grow them but it was not possible. The current season proves to be otherwise. Stevia looks like a common weed at first. In fact I had my doubts when it began growing. To dissipate my doubts I munched a little leaf, and for my surprise it tasted sweet. Sweet home Alabama.(We are in Texas tough).
In its native South America, stevia is a perennial. Remember that a little frost will kill it.
Update. I moved the plant to four hours sun in the regular soil two months ago. The direct sun with high humidity around here seems to dislike this plant. It’s still alive, although it had a setback and now seems to be recovering. Anyway is one of those plants that don’t like our weather very much. I prefer to buy stevia packets in the superstore instead of growing this plant for sure. Stevia plant is a no-no for me around here.