Well, I will recommend that you use Google Search Console or other third party SEO tools to check which page or URL is treated as duplicate and then you need to check resource of these duplicated url and then by using robots.txt file or implementing a noindex you can fix this error.
Thanks
jackieasas commented: good +0
raj_41 commented: Thank you Gulshan. I will look in it. +0
12a7_02_Nguyễ commented: thanks you so much +0
FreelanceFin commented: Can't fault WooCommerce! +0
Gulshan_6 15 Newbie Poster
AndreRet commented: What error and on which line? +15