why I get a 500 error on a request for a OTCSticket - CS16.2

Kyle Huang

I use postman to send a POST request for OTCSticket http:// .../api/v1/auth?username=yyyyy&password=xxxxxx
but I get an http 500 error with the response ...

{
"error": "Argument \"username\" is required."
}

the GET is working fine.