After enabling the HTTP Event Collector (HEC) feature Cloud in Splunk trial, why am I getting no response from Splunk?

[splunkdemowec]

I have the Splunk Cloud trial. I've enabled the HTTP Event Collector feature as described here: http://dev.splunk.com/view/event-collector/SP-CAAAE7F

This enabled me to send data from Postman into Splunk. I tried to send a POST request using postman to Splunk but got no response.

method: POST
url : http://https://input-pr******.cloud.splunk.com:8088/services/collector
Authorization : my generated token

Am I missing something else?