Hi
Activation Lock prevents unauthorised use of Apple Watch if it is lost or stolen. If the previous owner has already followed the steps here to remove Activation Lock:
About Activation Lock on your Apple Watch - Apple Support
And if you are trying to pair it to a compatible model of iPhone, running the latest version of iOS:
Set up your Apple Watch - Apple Support
And you are being advised by the Watch app that the Apple Watch is still locked by Activation Lock, then it may help if you, as the new owner, try these steps:
- Close the Watch app on your iPhone:
On your iPhone: double-press on the Home button > swipe left / right to the Watch app > swipe up on the app preview to close it.
- Restart both devices, turning both off together and then restarting your iPhone first:
- Try again to set up the watch:
If the Apple Watch remains locked, ask the previous owner to accompany you and the watch to a Genius Bar appointment, taking along their original proof of purchase for the watch or ask them to contact Apple Support and seek assistance with removing Activation Lock: