Full Answer

The silent-failure design is what makes this change dangerous. A WooCommerce store pulling 7-day view-through attribution into a Google Sheet or a BI tool won't get a 400 error or a deprecation warning — the API returns a valid response with empty values. Unless someone is actively checking whether the numbers make sense, the gap goes unnoticed while ad spend decisions are made on incomplete data.

For stores that relied on view-through windows to justify top-of-funnel Meta spend, the remaining 1-day view window captures far less of the customer journey. A shopper who sees an ad on Monday and purchases on Thursday no longer attributes to that impression. The 7-day click window still catches most direct-response conversions, but brand and awareness campaigns lose their measurable tail. That's a reporting gap, not necessarily a performance gap — the conversions still happen, they just stop showing up in Meta's numbers.

The fix: audit every reporting query, API call, and dashboard tile that references a view-through window longer than 1 day and switch it to a supported window. Meta's January 2026 API change has a full breakdown of which endpoints are affected and how to update them.