If you are having issues with stock not updating for a 'child' product in a variation listing, the most common reason can be because the child product SKU is the same as the parent product SKU.
If this is the case then the child SKU stock levels will not be updated correctly.
To resolve this please amend the parent SKU number in the marketplace and re-download this product into Selro. This should resolve the issue.
If you have any questions regarding this process please feel free to contact our support team at firstname.lastname@example.org