Find out why lead IDs are being rejected

Lead conversions are keyed on the Meta lead ID rather than on an email address, so a lead with a missing or malformed ID cannot be reported back however complete the rest of the record is. This article covers what to check yourself and what to ask support for.

What the lead ID is

A 15 or 16 digit number that Meta issues for every lead. It arrives in the leadgen_id field on the lead generation webhook. Where it ends up after that depends on how the lead was downloaded or synced into your CRM, so confirm which field yours actually holds it in rather than assuming.

Check the field type first

The single most common cause is a numeric field. A 16 digit number stored in a numeric field can be truncated or rounded, and the resulting value looks plausible and matches nothing. The field has to be text.

Check the lead actually came from a lead ad

Only leads generated by a Meta lead ad campaign have a Meta lead ID. Records created manually, imported from a list, or captured by a form on your own site do not have one and cannot be reported through this integration. If your CRM mixes sources, filter the export to lead ad records.

Check the form configuration has not changed

Confirm the form IDs configured in Studio are the current ones. An old or inactive form ID receives nothing new.
If a form was rebuilt or its fields changed mid-campaign, the mapping needs revisiting.
If a form was paused, leads stop arriving from it.

Check access has not lapsed

Lead retrieval depends on a token tied to Page access. If the person who authorized it lost that access or left, retrieval stops. Regenerate it as a system user token rather than under an individual account, so it does not depend on one person remaining in post. Separately, an ad account or Page that has been restricted loses lead access entirely.

Check your CRM is not discarding them

Some CRM configurations silently drop a lead when the email address already exists. Others truncate long answers where a field has a character limit, or refuse the record outright when a mandatory field is empty. In each case the lead never reaches the CRM, so there is no ID stored to send back.

Still stuck

Contact support with the project, the instance and the date range, along with a sample of the records you expected to be reported. Most of the causes above show up in one.