Useful Tips

The Virtuemart Products should have prices to be displayed inside the PB groups. A price can be zero (0) or negative but not null (blank). Except the child products which can take their price from the parent.
A product should be published.
If stock check is is used within Virtuemart, the product should have stock.
Each used product should belong at least to 1 category. Except the child products which can take their category from the parent.
When there is not even one product that can be displayed in a group, that group won't be displayed in the front-end.
Only Custom Fields which are set as "Cart Attribute" and "Cart Input" are being loaded by Product Builder.
To use custom fields to select the child products of a product, you can use either the Child Variants (Virtuemart 2.x) or our Stockable Custom Fields (Virtuemart 3.x)
If you want to display the selected products from custom products, grouped in your cart/checkout pages, please have a look at that free solution:
https://github.com/Dudebaker/Breakdesigns-Product-Builder-System-Plugin