Form fields are not compatible with dynamic checkout buttons on product pages. If a customer uses a dynamic checkout button like “Buy It Now,” their answers to the form fields will not be collected. For the fields to work, customers need to use the standard Add to Cart button.
To disable dynamic checkout on a product page template:
In your Shopify admin, go to Online Store > Themes.
Find your theme and click Customize.
Open the drop-down menu at the top of the page and select Product.
Choose the product template used by products with fields.
Select the Buy buttons block.
Make sure Show dynamic checkout buttons is unchecked.
Click Save.