Make sure that you’ve implemented Firebase Cloud Messaging SDK according to this instruction.

Pay your attention and implement the first three paragraphs of this part of the instruction (in case you disable the method swizzling, the paragraph about disabled method swizzling is also mandatory).

Make sure that the app resolves images in push notifications.

There are 2 ways to send a push_token to Amplitude: via event + event_property, or via user_property:

We strongly recommend triggering the push_token event logging on EVERY app start

NOTE. In case you use Firebase Push SDK, make sure that you send Firebase registration id (which is also referred to as fcmToken in code examples). Do not confuse it with the APNS push token. The one we need looks like this: