Apple watch

Activation Lock is designed to prevent anyone else from using an Apple Watch if it's ever lost or stolen.

About Activation Lock on your Apple Watch - Apple Support

Activation Lock is an anti-theft feature that cannot be bypassed. Only the previous owner can remove the lock by using their Apple ID & password. Apple will not help you find the previous owner. If the previous owner cannot or will not remove the lock, then the watch is useless to you or anyone else. Try to get a refund (through eBay) or dispose of the watch properly. In the future, see the 'Before you buy a watch from a third-party' section in:

What to do before you sell, give away, or trade in your Apple Watch, or buy one from someone else - Apple Support

The only person who can unlock the watch is the person who locked the watch. Apple will NOT help you. We cannot help you. Either get the person who locked to the watch to unlock the watch, or if you can't, get your money back. You've most likely been scammed. People come here every day, often multiple times a day who bought an activation locked watch. Most of them are stolen. And they've totally wasted their money.

If you can't get the person to unlock the watch, nor get your money back, recycle the watch responsibly as there is no help available to you and the device is useless.

Read this --> The All Too Common SAD Reality of Buying … - Apple Community

If you are able to contact the seller you could ask them to remove the watch from their Apple ID and release the lock. However, you are asking here so I suspect this is not an option and you are equally unlikely to be able to get a refund. ☹️

The only person who can release Activation Lock is the original owner who set it. If you can't contact that owner the watch is useless and can never be reactivated. Your only remaining option would be responsible recycling.