title: Invalid key in checkin plist: GMSInstanceIDDeviceDataVersion
body: <p>So I followed google's GCM for iOS tutorial <a href="https://developers.google.com/cloud-messaging/ios/start" rel="nofollow">here</a> but for some reason it wouldn't send notifications to my phone.</p>
  
  <p>I successfully registered with GCM when it asked on my device and when I send the message via their demo, it says it was sent successfully but it unfortunately was never received.</p>
  
  <blockquote>
    <p>2016-04-12 20:58:22.999 GcmExampleSwift[443:]  App measurement v.2003000 started
    2016-04-12 20:58:23.002 GcmExampleSwift[443:]  To enable debug logging set the following application argument: -GMRDebugEnabled
    2016-04-12 20:58:23.049: GCM | GCM library version 1.1.4
    2016-04-12 20:58:23.221: GCM | GCM registration is not ready with auth credentials
    Could not connect to GCM: The operation couldn’t be completed. (com.google.gcm error 501.)
    2016-04-12 20:58:23.558 GcmExampleSwift[443:]  App measurement enabled
    2016-04-12 20:58:23.596: GGLInstanceID | Invalid last checkin timestamp in future.
    2016-04-12 20:58:23.632: GGLInstanceID | Unable to find token in cache Error Domain=com.google.iid Code=-25300 "(null)"
    2016-04-12 20:58:25.085: GCM | Invalid key in checkin plist: GMSInstanceIDDeviceDataVersion
    Connected to GCM
    2016-04-12 20:58:25.431: GGLInstanceID | Unable to find token in cache Error Domain=com.google.iid Code=-25300 "(null)"
    Registration Token: XXXXXXXXXX
    2016-04-12 20:58:26.578 GcmExampleSwift[443:62016] Subscribed to /topics/global
    2016-04-12 20:58:38.731 GcmExampleSwift[443:]  Fetched configuration. Status code: 200
    2016-04-12 20:58:38.731 GcmExampleSwift[443:]  Successful fetched configuration from the server. Got network response. code, size: 200, 124</p>
  </blockquote>
  
  <p>I noticed there was the issue <code>Invalid key in checkin plist: GMSInstanceIDDeviceDataVersion</code>. I'm not really certain this is the ticket, but it's difficult to determine what the issue is exactly when GCM says everything was successful.</p>
  
  <p>Thanks!</p>