A problem is not automatically a business opportunity just because someone complains about it. Learn how to test its frequency, cost, existing workarounds and buyer ownership before deciding what to build.
Use Google Keyword Planner, Trends and real search queries to understand a problem, identify existing solutions and research SaaS product opportunities before building.
You don't need a working product to test demand. You need evidence that a specific group has a real problem, already tries to solve it, and is willing to take action for a better solution.