402 stands for Authentication Failed. In other words, the credentials (username / password) provided in the request are not valid. The details tab in the Gateway Audit Events log will identify the service that the request was submitted to (/foo/bar in this example).
Node : Gateway1
Time : 20190222 03:10:51.459
Severity : WARNING
Request Id : 123456789123456789
Message : Message was not processed: Authentication Failed (402)
Audit Record ID: df564fd1va658aav6avdf4d5fds5fsdf4
Event Type : Message Summary
Client IP : 1.2.3.4
Service : fooBarService [/foo/bar]
Operation : getID
Rqst Length : <Not Saved>
Resp Length : <Not Saved>
Resp Status : 0
Resp Time : 0ms
User ID : <No ID>
User Name : null
The request tab may identify the username that was used in the request (john.doe in this example).
<UserId>john.doe</UserId>
The response tab should identify that the credentials are invalid.
<?xml version="1.0" encoding="UTF-8"?>
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/">
<soapenv:Body>
<soapenv:Fault>
<faultcode>soapenv:Client.InvalidCredentials</faultcode>
<faultstring>Resubmit using the correct credentials</faultstring>
<!-- <detail>A problem occured processing the request</detail> -->
</soapenv:Fault>
</soapenv:Body>
</soapenv:Envelope>