I've come to realize that just because people express problems, doesn't mean they'll do something about it. You need to find something where the pain is urgent, and unsurmountable. And that's very tricky.
As you noted earlier, the tech is the easy part. As you note here, finding customers is the hard part.
Naturally doing the easy part first can often turn out yo be a waste of time.
You talked above about "your ideas". Don't start there. Start by walking around talking to people. Start in your local community. You're looking for pain, and a willingness to pay. Yes, it's the hard part. Yes it's work.
Just a few of the things I learnt from that book:
Don't ask if people would use your product. It's too hypothetical and people are too nice. "Sure, I'd probably use it. Looks useful. Keep working on it!". Then you never hear from them again. If you really think they'd be interested, ask for money.
Don't ask about people's problems in an abstract way. "Tell me about your business problems" is just too vague and wishy-washy. Ask about more specific things. Example: "You're having issues with double booking? Tell me about the last time it happened." Asking about the most recent time something happened is a great way to get concrete details.
Ask people how they have solved the problems or tried to solve the problem they talk about. "It was a major issue so we hired an extra member of staff to confirm all the stock lists". (Great, they're willing to spend real money on fixing this). "I searched around and tried out ABCSoft and XYZSoft but they were designed for a different kind of business and didn't really solve it for us" (pretty good, they're putting effort into finding solutions). "Oh, well, it's always been a big issue but we haven't tried to solve it yet" (Uh-oh, it's probably not really a big problem for them. It's not painful enough for them to try to solve).