Everything is automated, so having a chat with eBay is unlikely to achieve anything that you won't achieve by following the set procedures.
If your seller cancelled the sale without a valid reason (which does not include discovering faults with the item) they will receive an account defect. You should also be able to leave feedback (apols if you've already done so, but I can't check as it isn't working).
Presumably they have refunded you? If not, you need to use eBay's money back guarantee.
Don't expect buying from strangers on eBay to be like the shops. eBay is a jungle. They even warn buyers in the user agreement that "they do not guarantee the existence, quality, safety or legality of items advertised, or the truth or accuracy of descriptions". Would you have bought this expensive drone from a shop that said this? That it could be untruthfully described, poor quality, unsafe or even illegal?? You may have had a lucky escape - I wouldn't even thinking about buying a drone of that value from a stranger here.
Don't build too much into eBay's eBay's "buyer protection". It doesn't guarantee that the seller will complete the sale, probably won't help if it's delivered to the wrong address and it sn't a warranty - it only lasts for 30 days anyway. From day 31 if it goes wrong or turns out to be stolen, eBay will have no interest.
