Merchants in the EEA, UK, and Switzerland may experience disapprovals or limited visibility in free listings if they have not explicitly chosen a Comparison Shopping Service (CSS).
This requirement is outlined on an updated Google help page, emphasizing the necessity for merchants to select a CSS in their Merchant Center settings.

The update adds a section titled Select a CSS for Free Listings in Europe, stating that not choosing a CSS may lead to product disapprovals or limited visibility. Merchants need to navigate to Settings > General > Comparison Shopping Services > Free Listings in Europe to choose between Google Shopping or a third-party CSS. Only one CSS can represent a domain, and once selected, synchronization may take 24-48 hours to clear any disapprovals.
Read the official help page found by Hana Kobzová: Comparison Shopping Services (CSS).