Yes, hard lemonade can be a real tough ferment to get going, due to the high acidity level. I'll see if I can find the specific thread I had from a year or more ago talking about how to get it going.
Check your lemonade container- what are the ingredients listed? If one of the ingredients is potassium sorbate, or just sorbate, it won't ferment. That's a preservative. Frozen canned lemonade tends to not have that.