Issue

When using the Google Ads Conversions destination in Segment, you may encounter the error: 400: External Audience ID is required while trying to use the Customer Match User List action. This error appears when mapping data from a standard source connection where there is no field to enter the required audience ID.

Product

Twilio Segment

Environment

Segment Console

Cause

This error occurs because the Customer Match User List action requires an External Audience ID, which is only provided when the action is triggered by an Engage Audience or a Reverse ETL source. Standard source connections do not supply this ID, resulting in the error.

Resolution

To resolve this error, use one of the following supported approaches:

Option 1: Engage Audience

1. In Segment, go to your Engage Audience and select Add destination.
2. Choose your Google Ads Conversions destination.
3. In the setup, disable Send Identify and enable Send Track.
4. Go to the destination’s Mappings tab and click + New Mapping.
5. Configure the mapping for the Customer Match User List action and save.

Option 2: Reverse ETL Source

1. In Segment, navigate to your Reverse ETL source and select the model you want to sync.
2. Click Add Mapping and choose your Google Ads Conversions destination.
3. Select the Customer Match User List action and pick a sync mode (such as adding or removing users).
4. Select an existing Google List ID (or provide a name to create a new one), map your External ID types, and set your sync schedule.
5. Enable the mapping to start syncing your warehouse records to your Google Ads list.

Additional Information 

Using Engage Audience or Reverse ETL ensures the required External Audience ID is included, allowing the Customer Match User List action to work as expected. For more details, refer to the Segment documentation on Google Ads Enhanced Conversions.