Architect GetExternalContactAction returning empty array for valid phone

Architect & Flows
1

I’m trying to use the GetExternalContactAction in Architect to look up a customer by phone number. The endpoint returns a 200 OK, but the contacts array is always empty, even though the number exists in the target system. Here is the configuration JSON:

{
 "method": "GET",
 "path": "/api/customers?phone={contact.phoneNumber}",
 "headers": {
 "Authorization": "Bearer {token}"
 }
}

The token is valid and the path resolves correctly. Any ideas why it’s not finding the record?