The category names you’re using at your platform might not, in most cases, be the same as the ones used by the channell you wish to have your products published at.
This means you have to find out which channel related category have the best match with yours, according to the channel categorytree.

Example, if you’re selling furnitures like coffee tables, you’ll probably have a Coffee table product_type in your platform. But the channel doesn’t handle this kind of category. The closest channel product category could be Kitchen & Dining Room Table. So this should appear this way in your data feed:

Furniture > Desks & Tables > Kitchen & Dining Room Tables

Boostmyfeed provides you an easy way to input the specific product categories matching yours.

Simply use your product_type field to map up with the categories. You’ll find this feature in the “category mapping” tab at your feed page.