Its not their problem, its the whole thing around it. As soon as the seller presses "refund" on the paypal website, there is a whole process started at paypal that gives a "bad user feedback" to Ultimaker, which ultimaker has to respond with putting at least 10% of their 3-month income to paypal as a "guarantee", and some other crazy loopholes that made companies wish customers never used paypal in the first place.
I had similar experiences with paypal before: Merchant accounts frozen for over 3 months (and no way to get a refund), credit card companies blocking accounts due to high paypal amounts going in/out, accidental refunds causing the whole sharingans of idiocy going skyhigh. One refund caused a small indie developer team to almost go bankrupt (Project Zomboid). As soon as a customer presses the "refund" button, the seller will end up in a kafka loop of pointless calling to an answering machine, which they would like to prevent.
Also, all dutch companies have a 7 day guaranteed refund after sale. Best is to send a message that you want a refund, make sure you mention that you give them 14 days to reply (standard time in here) and then file a claim at paypal stating that they never delivered the goods.
Refunds can take upto 3 months at paypal. Its not the seller's fault, its the anti-fraud system of paypal. I only had to do 2 refunds, which took around a week or 2 to show up on my paypal account (not on my bank account).