You identified both mistakes: you explained first, and you asked hypothetical questions. Fix those two and the next four conversations are worth more than the first five.
Ask about the past, not the future. People are unreliable about what they would do and quite reliable about what they did.
Bad: would you use this. Would you pay for this. Do you like it.
Good: when did you last have this problem. What did you do about it. How long did that take. What did you try before. How much did that cost you.
If somebody cannot remember the last time they had the problem, that is your answer regardless of how positive they are about the product.
Do not explain it first. The moment you describe what it is for, you have told them what to say and removed your only chance to see whether it is comprehensible. Put it in front of them and say as little as possible.
Ask about their problem before showing anything. Ten minutes on how they currently do this thing, before they have seen your solution and started being nice about it.
And a rule that changes the tone completely: tell them you are trying to find out whether to stop. People are far more honest when the encouraging answer is not obviously the kind one.