# 48003: Callback returned an invalid response

Log Type: APPLICATION

Log Level: ERROR

## Description

### Possible causes

* Your Frontline integration service returned a response which is invalid.
* Your service returned a response that was too large. Responses are capped at 64k.

### Possible solutions

* Make sure that callback returns a valid JSON which has the required fields that are defined in Frontline Docs.
* Make sure that your response size is less than 64k.