As a seller using PayPal, there is a possibility that a client might not be happy with your product/service and that they could dispute the payment. Whilst this is not common, PayPal does provide you and the customer with a system called the Resolution Center to assist both parties.
This can be found by going to the Activity section at the top of the screen and clicking Open Cases under Resolution Center.
Here you'll be able to see any open disputes.
If you do not agree with the dispute, you can respond to it with evidence that Payhip can provide you. To find this evidence, go to your Customers section and find the customer who started the dispute. From there, click learn more. This will open up a screen where you'll be given a lot of the details about the sale, including the date/time of the download as well as their browser and IP address. Take a screenshot of this to submit as evidence to PayPal.
You can then respond to the dispute via the resolution center, attaching the screenshot, which should help PayPal to cross-reference this information with the transactional data that they have. Click Submit to send off your response.
You'll then see the following confirmation screen.
Please be aware that you will only have 30 days to dispute the claim before PayPal will automatically refund the buyer.