If they request a refund, that is up to you how you wish to proceed. You could issue the refund or you could deny it. That is your call. If they do a chargeback, you better have a strong case as to why they do not deserve the refund. Assuming you are talking about your $1 resource, if someone asks for a refund and they have a strong case, ie: resource is advertised to work on 1.15.x but does not ... I recommend just given them the refund. I have never sold a resource but I heard that if someone does are a chargeback and it goes thru, PayPal charges you a $20 chargeback fee, is that really worth it over a $1 resource?
Mind you, if someone charges back - regardless of the result, they lose access to all future updates of the resource.
It depends If the plugin wasn't working at all and you had a very good reason to refund it, you probably would get the refund But if it was a perfectly fine plugin and you just said you didn't want it anymore i'm pretty sure that's a no I've gotten a refund from an author before and kept the download, it's up to him.