What is it?
In the new Stripe version, you will most likely encounter payments marked as Incomplete. Not to worry, this is to be expected. It means exactly what is says - the order was not completed. Each time someone comes to your checkout and Stripe has shown its UI on the checkout, it creates a "payment intent". When no transaction is made, it leaves an Incomplete entry in your transaction list. The reason that these payments are created is because of the transition from the legacy Stripe Elements to the newer PaymentElement. With the new PaymentElement, a PaymentIntent must first be created before the element is displayed.
Make the most of it
Use this opportunity to note who the User with the incomplete transaction is and indulge them to come back. You can click on the Incomplete payment and see the details in the metadata section. If this User left their email address in the checkout, it will appear.
Use this to your advantage and offer them a discount code in order to tempt them to come back and finish their order.
You can also setup an abandoned cart automation that picks up those left orders and sends them a sequence of emails to reach an order completion.