title: FCM Token is not generating in some android devices
body: <p>I was having issues in GCM, so i migrates to FCM but I am still getting issues related to token.</p>
  
  <p>I launched my updated app and I checked that there is 300 new users,
  200 of them are getting tokens and 100 are not getting any token, it's a very critical issue.</p>
  
  <p>Any Solutions of null token?</p>