You can use a copy like Oops, it looks like our product wasn't right for you. Please tell us what you would like to see improved.
Leave a space below the text where the buyer can answer or ask some specific questions to get exactly the answers you are looking for.
This feedback will help you understand why visitors did not decide to purchase, and you can use it to improve your product to make it even more attractive.
You can see how Zen Mountain does this. After the main question, germany phone number there is a friendly request to visitors to help them find what needs to be improved.
Generally, most of them have Fomo . You can use this FOMO moment to your advantage. Various promotions and discounts or signage like "Sold out soon" or "Only two left" encourage them to decide to buy as soon as possible.
This way you don't give them time to think and end up forgetting about the purchase.
Be sure to add the key benefits of your product to such a pop-up to present it as a great opportunity that may not be available the next moment.
Flash sales like this one on the SiteGround example can significantly increase conversion rates.