If you do a demo for your potential customers, and they say, "That's a great product. I can see how that would be really useful," you can safely assume that you're doomed.
Keep looking until your customers are desperately trying to write checks for dodgy prototypes.
The first few customers are not necessarily a market signal - they are often acquired via personal relationships or they want to leverage you to do custom development for them via your prototype. Neither of which are scalable businesses.
If you do a demo for your potential customers, and they say, "That's a great product. I can see how that would be really useful," you can safely assume that you're doomed.
Keep looking until your customers are desperately trying to write checks for dodgy prototypes.