Firebase (Notification Service)
- Make sure that you’ve implemented Firebase Cloud Messaging SDK according to this instruction. 
- Pay your attention to the first two paragraphs of this part of the instruction. The third paragraph is optional. 
Amplitude (Integrate Analytics)
- There are 2 ways to send a - push_tokento Amplitude: via- event + event_property, or via- user_property:- [Recommended]. Implement setting a user_property - push_tokenusing the identify method
- Implement sending events in Amplitude: you need to send a - push_tokenevent with an event property- push_token, in which the device token from Firebase is passed.
 
- We strongly recommend triggering the - push_tokenevent logging on EVERY app start.