How to Subscribe to some to Community Event?

Hi,

I am trying to subscribe to UserUpdate event as per the following article-

http://community.lithium.com/t5/Developers-Knowledge-Base/Subscribing-to-community-events-using-the-REST-API/ta-p/14785

After following the instructions, my url becomes-

http://community.optimizely.com/company/restapi/vc/events/subscriptions/events/name/UserUpdate/subscribe?restapi.session_key=123456789&event.callback_url=https://community.mycompany.com

And when I make an Http callout using this url, I get "Page Not Found Response"

But when I use the following URL to register to User Update event i.e. without tennant-

https://community.optimizely.com/restapi/vc/events/subscriptions/events/name/UserUpdate/subscribe?restapi.session_key=123456789&event.callback_url=https://community.mycompany.com

I get the exact response which is given in the documentation, so I assumed that I have subscribed to UserUpdate event-

<?xml version="1.0" encoding="utf-8" standalone="yes"?>
<response status="success">
<value type="string">e73e395b-bca6-4d90-8956-cff93d20828e</value>
</response>

(The above ID is obviously different in my case case)

But when I make some update in my User from the community, my event does not get captured and callback URL is not called as a response.

Kindly guide, what I am doing wrong.