If your add-on fields are not showing as expected, please check the following:
- You have entered a price for the product, even if it’s 0. The product will only show the cart form, where the add-on fields are located, if the product has a price. You can find out more about the price label here.
- Ensure that your theme includes the
woocommerce_before_add_to_cart_buttonaction hook. A quick way to check this is to switch to a default theme like Twenty Nineteen and retest. If the fields display with the default theme but not with your theme, then it’s likely your theme is missing this hook.