Issue Setting Up Apple Watch Cellular - "Couldn't Sync iCloud Data" Error

I have spent two days trying to set up my new Apple Watch Cellular with my iPhone 15, but I keep encountering a persistent issue. When attempting to configure the watch, I receive the error message: “Couldn't sync iCloud data,” with options to either cancel or delete iCloud data. I have repeatedly selected “Delete data,” but nothing happens, and the Apple Watch app on my iPhone simply displays a “Server error” message.

At this point, I’m frustrated and disappointed. I’ve spent £500 on a product that I can’t even use. Both my iPhone and Apple Watch are updated to the latest iOS, so I expected a smooth experience. This watch doesn’t reflect the usual Apple quality—it feels like a rushed cheap product, and I'm frankly fed up. Apple's products are deteriorating.