...the product pages doesn't seem to rank in search engines.

Setting a rel="canonical" is unlikely to help your ranking if you aren't currently being ranked already.

Setting a rel="canonical" tag informs search engines which of the two (essentially duplicate) pages should appear in search engine results (SERPs). If you don't specify this then the search engines will decided for you... one or the other, which might not be the one you wanted.

If you have a preference as to which page should appear in the SERPs then that is your canonical page and the other page should include a rel="canonical" tag pointing to the former.

...the product pages doesn't seem to rank in search engines.

Setting a rel="canonical" is unlikely to help your ranking if you aren't currently being ranked already.

Setting a rel="canonical" tag informs search engines which of the two (essentially duplicate) pages should appear in search engine results (SERPs). If you don't specify this then the search engines will decided for you... one or the other, which might not be the one you wanted.

If you have a preference as to which page (of two essentially duplicate - or very similar - pages) should appear in the SERPs then that is your canonical page and the other page should include a rel="canonical" tag pointing to the former.