In my magento2.1.5 (migrated from magento1.9) store, some configurable products are not showing any associated simple product in both admin and front-end. I need to set the simple products again in admin and then it is working good. This behavior is repeating in products that are migrated from magento1.9.

Strange thing is, when I get the children of that configurable product using code below, it is showing me the child products.

$  children = $  product->getTypeInstance()->getUsedProducts($  product); 

It looks like the simple products are associated but somehow magento is not able to render this.

I also checked the values in database and for most products having issue, the value of “has_options” and “required_options” is set to 0. Changing it to 1 doesn’t work for me.

These products were working fine earlier and is working fine on my older staging deployments. Can anyone please tell me what is the issue?