title: Why do I get "MismatchSenderId" from GCM server side?
body: <p>I'm trying to create a push service for my Android app, and I follow Google GCM's documentation and example for this matter:</p>
  
  <p>I can register/unregister my Android app. From my server side, I can see that I have one subscription registered, but when I try to send a message from server to my Android app I always get following error:</p>
  
  <blockquote>
    <p>Error sending message to device #0: MismatchSenderId</p>
  </blockquote>
  
  <p>For my Android app, I use SENDER_ID = 200000000001.</p>
  
  <p>And for my server side as Google says I use API_KEY = AIzxxxxxxxxxxxxxxxxXxxXxxXxxxXXXXXxxxxs</p>
  
  <p>I followed this document: </p>
  
  <blockquote>
    <p><a href="http://developer.android.com/guide/google/gcm/demo.html" rel="noreferrer">http://developer.android.com/guide/google/gcm/demo.html</a></p>
  </blockquote>
  
  <p>I've enabled GCM in my Google API panel too, yet I'll get that annoying error message.</p>
  
  <p>How can I fix this problem?</p>