Common Facebook CAPI Errors and How to Fix Them

Why CAPI Errors Are Easy to Miss

Facebook CAPI errors are often silent — the API may return a success response even when the event is not processed correctly by Meta. Unlike browser-side pixel errors (visible in browser DevTools), server-side CAPI errors require active monitoring to detect.

Error 1: Invalid Access Token

Symptom: API returns error 190 or "Invalid OAuth access token"

Fix: Regenerate the access token in Events Manager → your Pixel → Settings → Generate Access Token. Access tokens can expire if the connected user's account password changes or if app permissions are revoked.

Prevention: Use a System User access token (created in Business Settings → System Users) rather than a personal user token. System User tokens do not expire when individual user passwords change.

Error 2: Wrong Pixel ID

Symptom: API returns error 100 or "Invalid parameter" on the Pixel ID

Fix: Verify the Pixel ID in Events Manager → your Pixel. The ID is a 15-16 digit number, not the "Pixel Name." A common mistake is using the Ad Account ID instead of the Pixel ID.

Error 3: Invalid Hash Format

Symptom: Events are received but EMQ score is very low (2-3) despite passing email and phone

Diagnosis: Events Manager → Diagnostics tab → look for warnings about customer information parameters

Fix: Verify hashing is done correctly:

• Email: lowercase, trimmed, SHA256 hex digest — NOT base64, NOT MD5
• Phone: all non-numeric characters removed, country code included (no +), SHA256 hex digest
• Do not double-hash: hash once, not hash(hash(email))

Error 4: Missing action_source

Symptom: API returns error "action_source is required" or events not appearing in Events Manager

Fix: Add "action_source": "website" to every CAPI event payload. This field is required and tells Meta where the event originated.

{
  "event_name": "Purchase",
  "event_time": 1735682400,
  "action_source": "website",  // Required — add this
  "event_source_url": "https://yourstore.com/order-confirmation",
  ...
}

Error 5: event_time Out of Range

Symptom: Events appear in API response as successful but do not appear in Events Manager or in campaign attribution

Fix: The event_time must be a Unix timestamp within 7 days in the past and no more than 1 hour in the future. Check that your server's system clock is correct and that event_time is a Unix timestamp (integer seconds since epoch), not a formatted date string.

Error 6: Duplicate Events Without Deduplication

Symptom: Reported conversions in Ads Manager are approximately double your actual transaction count

Fix: Implement event_id deduplication. Both browser Pixel and CAPI events for the same action must carry the same event_id. For purchases, use the order ID in both the fbq() call and the CAPI payload.

Error 7: Events Not Being Attributed to Ads

Symptom: Events appear in Events Manager but show no ad attribution

Fix: Check that fbp and/or fbc cookies are being sent. Without these, Meta cannot link the CAPI event to a Meta ad click. Capture _fbp cookie from the browser and pass it in the CAPI user_data. For traffic from Meta ads, also capture and pass the _fbc cookie (set when a user clicks a Meta ad link).

Summary

The most impactful CAPI errors to check: incorrect hashing format (lowercased email, numeric-only phone, SHA256 hex), missing action_source field, event_time being a formatted string instead of Unix timestamp, and missing event_id causing duplicate counting. Monitor Events Manager Diagnostics tab weekly — it surfaces data quality warnings that are not visible in API responses.

See our Facebook CAPI Setup service for error diagnosis and fixes.

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