To confirm you are getting the 202 in response to your POST request?
Perhaps add a
server.post('*', function(req, res) { console.log('got a post'); });
Or similar to see if there is a fault in your
userData.followHook
And if you could post in full rather than snipped, I can check the whole program, but I think the fault lies in your callback that you are passing. In your challenge response you should also be able to dump out the headers to confirm those with what you sent