This applies when Shopify products are created, but the expected variant option labels or values are missing, messy, or assigned to the wrong products.
Work through these checks
Does the linked attribute have a value on that product? If the source field is empty in the grid, Shopify cannot create the variant value.
Is the option scoped to the right products? If the option should only apply to some products, limit it correctly instead of leaving it effectively global.
Are the source values clean enough for Shopify display? Messy source values create messy Shopify variant labels. Standardize the underlying attribute values first.
Are you creating more combinations than the product really needs? If variant output looks broken or overcomplicated, reduce the number of dimensions to the ones that matter.
Success check
Shopify shows the intended variant option labels and values.
The option only appears on the products that should use it.