Error: 

The message could not be delivered to the device identified by 'eeRC8-X_QcurZwVvssrSCf:APA91bEK_HrxYMbiUCu2ntF21hqB5uv5w6GTet_J3cMtA-QJAhrRvuwlrlJMM2Sfr5wwkVV-tpcPtB34Gd1IofOMz5078G64XufPbnTZ49p2rRuixXjmW_c'.

Although the token is syntactically correct, it is not known to the Firebase
project you are using. This could have the following reasons:

- The token has been unregistered from the project. This can happen when a user
  has logged out from the application on the given client, or if they have
  uninstalled or re-installed the application.

- The token has been registered to a different Firebase project than the project
  you are using to send the message. A common reason for this is when you work
  with different application environments and are sending a message from one
  environment to a device in another environment.