Trying to retrieve the wunderlist lists with HTTParty

gistfile1.rb

# After authenticating with OAuth and getting the auth object
response = HTTParty.get('https://a.wunderlist.com/api/v1/lists',
        headers: {
          'X-Client-ID' => "#{auth.uid}",
          'X-Access-Token' => auth.credentials.token
})

# response will look like so at the moment:
# <HTTParty::Response:0x7faf31dad288 parsed_response={"server_unavailable"=>true}, 
# @response=#<Net::HTTPServiceUnavailable 503 Service Temporarily Unavailable readbody=true>,
# @headers={"cache-control"=>["max-age=0, private, must-revalidate"], "content-type"=>["application/json"],
# "date"=>["Sun, 31 May 2015 08:14:52 GMT"], "server"=>["nginx"], 
# "x-request-id"=>["XXXXXXX"], "content-length"=>["29"], "connection"=>["Close"]}>

# Is this an HTTParty issue? What am I doing wrong here?