Apple Watch Apple ID lock

Dear people, I bought an used Apple Watch Series 5 Nike and an iPhone 11 Pro Max, I got the boxes, and the I have the bill for the watch too. Unfortunately the Apple Watch has an Apple ID lock from the previous owner, I asked him to remove the watch from his iCloud but he couldn’t log out from the device. I asked the apple support, I sent them a photo of a bill and a photo of the back of the watch box. I don’t have any answers and the watch is still locked, I spent much money on that watch and I’m really worried about that I won’t be able to use it. It’s so bad that I know the old owner but I can’t use the watch because of his lack of skill at IT. Any ideas what can I do?