Apple Watch reset

You can't reset it;

The person that you bought this watch from needs to follow all the steps in this link;

Prepare the watch so the buyer can use it.

If they can't or won't then get your money back or recycle the watch and put it down to experience.

Hello:) If you cannot arrange for the previous owner to do this, then you should, if possible, return the watch for a refund.

You will not otherwise be able to use the watch. There is no way around this security feature.

Apple will not advise you of the previous owner's contact details, nor will Apple pass your details on to them.

More information:

About Activation Lock on your Apple Watch - Apple Support

~Katana-San~