Sales can sometimes be poor indicator of the success of your product.
In the early stages of your company, don't despair if you don't make any sales. The problem isn't necessarily the product. Making the box blue, or adding a new feature will not magically boost sales. Instead look at the process you used to sell it.
Two things will help you create sales.
Is your product too new for the user? Do they even understand the problem you are solving for them? When the first elevators that didn't require an operator where dispatched, people were furious. Why should a gentleman in a suit operate an elevator? Or a gently born Lady be reduced to pressing buttons on a machine?
It's not that elevators were hard to operate, but it required a culture shift to make it OK for non-elevator-boys to press the button.
Are you selling thick fur jackets, in summer? Or a USB-C Phone in 2005? In the real world timing is a little more subtle than that, a lot of other factors have to come together to make your product a success. It is one thing to try to polish your product, it is another to look at the world in which you are dropping your product.
The users may like your product, even see themselves using it... in the future.
Timing is a hard problem to solve, and sometimes it is out of your hand. But something can be done.
Think of Pepsi and Coca Cola. When was the last time they innovated? Instead they focus on telling a story. Every few years or so they try to send a new message to connect with the new generation. At the moment, Pepsi made a botch of it with its latest protest ad, they still sell the same sugar water, but the story they told ruined their image.
In the 70s, Coca Cola told a new story with "I'd like to buy the world a coke", it became one of the most critically acclaimed commercial. Their product never changed, they still sell sugar water.
Now think about your product. Does it work? Does it deliver in what it promises? Good. Now all you have to do is to work on your story. No need to turn the box blue, red, white or anything. Think of the person that will consume your product and write a narrative starting there.
If you never made any sales it's because the user doesn't relate to your narrative. Fix the story and you will see that first sale.