Add Product quantity option misaligned on product archive

Hello

I have bought the plugin ‘Product variation swatches’
When the ‘add product quantity option’ is selected the option is pushed to the side.

I know this a css issue but have little time to investigate.

The first image has centre align this is because I have a sidebar (this is how I want it as default). The second image is archive without sidebar the product quantity option is not aligned.

I have included screenshots of the issue. Could you give some pointers how to fix this.

Many thanks