post https://api-sandbox.pismolabs.io/networktransactions/third/party/issuer-authorization
The documentation here details how zero balance customers should code their anti-fraud and validations webhook. Zero balance clients need to register this webhook with Pismo. This is not a callable endpoint from Pismo's API reference.
This webhook request to zero balance clients occurs during step 5 in the Full and zero balance workflows guide.
For more information, see Zero balance anti-fraud and validations integration.