If you set up Web Push notifications with Google Cloud Messaging API in https://console.developers.google.com then you need to import your project into Firebase, and then get the new Firebase Server key.
How to import your project into Firebase?
1. Log into https://console.firebase.google.com with your Google account.
2. Click on "or import a Google project"
3. Select the project:
4. Click on "ADD FIREBASE" button.
How to get Firebase API key?
1. After project is imported, click on the Settings icon and then on "Project settings" link.
2. Then click on "Cloud Messaging" link:
3. Now copy the Sender ID and Server key:
4. Send Server key and Sender ID to your account manager or paste them in Push notification settings: