The goal is fast streamlined rejection. You want an enormous list of well defined rejections. Doing one more isn't a challenge. Getting rejected faster, more efficiently, more accurately and for better reasons.
Pretend you run their business, would the product be as useful as it was designed to be? To answer that question you need some information.
If your software is going to be super useful for an event that happens only 1 time per year and doesn't take much time to do manually you don't have to wait for them to explain this to you in their complex polite way.
If it is useful to them, can they afford locking themselves into the service? What happens if the product is discontinued? What will it cost to clean up behind you?
If there is a way out and they cant afford it you can still gain a free user but it might be better not to.
Every second you spend is a second not spend on the next prospect who might badly need your product. You want to waste as little of their time as necessary, when the task is completed it is completed for both parties. The goal was to figure out if it fits. When done you thank them for successfully completing the task.
You have to dial down your clock cycle to their working speed. It is your moment of relaxation. The real work is moving between such interactions as fast as humanly possible.