I Bought A Used Apple Watch And Its Locked. This resets your Apple Watch to the factory settings. Click the remove button next to your Apple Watch.

Click Erase Apple Watch. Before you buy an Apple Watch from someone other than Apple or an authorized Apple reseller make sure that the device is no longer linked to the previous owners account. I bought an Apple Watch series 2 from someone in OfferUp and was told everything works fine no issues once I got home and got it charged Apple Watch pairs fine but stuck on activation lock with someone elses iCloud I have reached the previous owner and no responses for a couple days now.
Erasing all content and settings erases all media data and settings from your Apple Watch but it does not remove Activation Lock.
You need to prove that the ownership has been transferred from the original owner to you. To check if the watch you purchased has an active iCloud Lock open the Apple watch App on your iPhone. Try Re-setting your Apple ID. Buying a used watch.

