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This warning appears in Facebook Events Manager when the FBC cookie value Upstack sends doesn’t match what Facebook has on file for that user. In most cases, it resolves on its own within 10–14 days. Most common cause: You recently switched tracking providers (Elevar, Triple Whale, Blotout, GTM, and similar). Returning visitors still carry old cookies from your previous provider, and Facebook flags the mismatch. As those cookies expire, the warning goes away.

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Other possible causes

  • You changed or swapped your Shopify theme, which reset the app embed configuration.
  • A redirect (age gate, A/B test, language selector) is stripping the fbclid parameter from URLs.

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What to do

  1. Wait 10–14 days. Monitor the affected percentage in Events Manager → Your Pixel → Diagnostics — it should decrease steadily.
  2. Make sure no old tracking tools are still sending events.
  3. If it doesn’t improve after 14 days, contact Upstack via Slack or in-app chat with your store URL and a screenshot of the diagnostic.
Does this affect ad performance? Usually no. Your events still reach Facebook, and other matching parameters (email, phone, IP, External ID) continue working. Click IDs are one of Facebook’s stronger attribution signals, so if a large percentage of events are affected long-term, it can reduce attribution accuracy.

What is FBC / Facebook Click ID?

Configure Meta Pixel destination

Disable Shopify Facebook data sharing

Enable theme app extension