Hi,
How do you know that the problem remains ?
I checked your product page, and the canonical URL is correctly added to the meta data of the page:
monosnap.com/file/P00Yseda9xsktQ7IKmYXm2m9wkX0p8
So you should not have the problem anymore once google scans again that page.
The goal of the canonical URL is that regardless of the URL google uses to access the product page, your website tells it that the canonical URL is the URL you want to be referenced for that page. So the only way you know whether the problem remains is to check the meta data of the page, and then see if google still finds an issue with that page when it indexes it again.
Adding canonical URLs won't mean that you'll get the same URL regardless from where you access the page.
You can do that if you want by activating the "force canonical URL on listings" setting of the HikaShop configuration, but that won't help for the "duplicate" error google shows you. It will just have the effect of have the same URL regardless from where you come for real users. It can potentially be interesting to do so, but it might also be interesting to not do so (for example, if you want to have a different breadcrumb on the page based on where the customer comes from).