I bought an apple what’s 2nd hand and I can’t get ahold of the original owner

Without the previous owner’s cooperation to follow the below-linked instructions, the watch will NOT work for you. EVER.

That might sound harsh, but they are the simple facts related to the intentionally-designed, theft-deterrent mechanism which you’ve encountered.

How to remove Activation Lock - Apple Support

The person that you bought/got this watch from needs to follow all the steps on this page;

Remove the Activation Lock so that the buyer can use it.

If they can't or won't then get your money back or recycle the watch and mark it down as a bad experience.

Neither the users on this forum or Apple can help you,only the original owner can help you.