Being lethargic doesn’t indicate if it’s good or not, it’s very individual, I’m not lethargic on SD for an example. I would give it 2 weeks, if you haven’t felt or seen anything by then I would toss it.
First time I used SD I thought it could be bunk also, didn’t see or feel any different, until 1 day I woke up looking like the day after Spider-Man got bit, like wtf happened over night?!
Hopefully yours is good so you get the same experience.