[sashimi0]

so i refunded a laptop a month ago and everything went well, i then sold it on ebay. everything was okay until today, buyer messaged me and told me that her apple ID has been blocked and she contacted apple, they told her that it was because the macbook wasn't pay for, it was a paypal chargeback as "not described" due to order number Wxxxxx.  she tried to create new apple ID but same thing, her laptop works fine tho just the apple ID part, any suggestion how to fix this?

That seems unlikely. Most likely what happened was that they purchased something on their own Apple ID and refunded or charge didn't go through on iTunes or App Store. A similar thing happens on a new Apple ID, especially if they're entering the same payment details on their old Apple ID.
They specifically quoted the order number? That doesn't sound like something they'd mention due to security.