I'm using Magento 2.2.2 and found a weird issue. When create configurable product with more than 1 attribute, the 1st child product not allow to select.
Attribute 1: Size (S,M)
Attribute 2: Color (Black, Blue)
When I create the configurable product with above attributes, Magento will auto create the child product:
The option for "Small + Black" not allow to choose, even with quantity or without stock control
Point to add-on. It only happen to "visual swatch".