You need to enable this widget by going to Product widget > Product Page tab:
The priority of enabling conditions
This app makes a priority for enabling conditions based on its order. Let me take an example for a better understanding of how the app works here.
You set to show up 5 products in the Frequently Bought together box. This app will check the enabling conditions sequentially to pick items to display in this widget. The first one is ‘Bought Together’ condition. If there is one product that satisfies the ‘Bought Together’ condition, the app will put this product to the list. Then it checks the second condition to choose 4 remaining items. If you haven’t set any products in the Manual recommendations, the app will check the third one. This app investigates the other conditions until it receives 5 products to put in the Frequently bought together widget.