The Cross Sell snippet is added to your theme files automatically. Sometimes this doesn't happen, because some themes use different names to identify their files; especially the product and cart files, which is where the Cross Sell snippet is added. 

Upon installation, the app searches for these files: 

• "product.liquid" / "product-template.liquid"
• "cart.liquid" / "cart-template.liquid" 

If any of these files exist, then the snippet would be added to them. If not, then the snippet would have to be manually added to the product and cart theme files.

Here is the snippet to add "{% render 'cross-sell' %}".

Manually adding the Cross Sell snippet

This will only take a few minutes, and we can help you do it if you are not sure how to proceed.