It is tricky to get the consistency down...and i am glad you are going to give it another chance.
The simplest way to make sure it is not set to hard is to hold it in your hand, if the Jello stays in your hand, then it is much too hard to whip them into the foamy consistency you are looking for. But no fear, all you had to do is put your Jello in the microwave for like less than 5 second and you are go to go.
Let me know whether i could assist further okay!