Amazon SNS: “Platform credentials are invalid” when re-entering a GCM API key that previously worked

Question

We have been using Amazon SNS to send Android push notifications since April this year.

Pushes have sent with no problem, however there has never been any record of

Answer 1

For those who are facing this in 2017, here goes a tip:

1 - Go to your firebase console (https://console.firebase.google.com/) click on your project (which you want to use for push notifications)

2 - Click on the "three dots" on the right side of your project name and click on "Settings"

3 - Click on "CLOUD MESSAGING" on the header tabs

4 - Copy the "Server Key" (this one is bigger than your API key)

5 - Paste on the "API Key" input of the AWS Form for "Create platform application"

PS: Note that this is valid only for GCM Push Notifications.