Products displaying in SERP instead of category and vice versa

Hi,

I'm running an online business but I can't give a link of the website because it deals with sensitive subjects.

Almost everything is OK on my website, product categories are ranking in SERPs and my usual SEO method is working.

But there's a product category page which doesn't rank for its keyword. In the SERPs, instead of this category, a product of this category is ranked, even if it's not optimized at all for the keyword. For example :

I have a category which is called "Viking Sweatshirts" and a product called "Black Viking Pullover with a golden collar". Every time I search for "Black Viking Pullover with a golden collar", the Viking Sweatshirts category is appearing 24th in the SERPs. And every time I search "Viking Sweatshirt", the Black Viking Pullover with a golden collar is appearing in the SERPs...

And this situation occurs for ALL the products within this category, even if the title tag doesn't contain the keyword... The category page is ranking in SERPs for all the products keywords (about 25th place every time), and a single product is ranking on the category keyword.

As the category doesn't contain the keyword of the product when I search, Google doesn't use my meta description and it's showing content of the page, so that it can find the keyword...

I know that every page needs to aim a single keyword, and that's what I do. My other categories don't have this problem, even if my method is the same !

I don't know what to do...

Have you every had this problem ?

Thanks !