Apple Watch

Advise that person to follow the advice listed in the paragraph titled "Turn off Activation Lock before you send your Apple Watch in for service, sell it, or give it away" in About Activation Lock on your Apple Watch - Apple Support

If not successful point out the link at the bottom of that Support Article:

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If it is "locked out from the person before," Activation Lock will permanently prevent you from using it. Only the previously registered owner can remove Activation Lock.