Send push to all devices requires Firebase Blaze (pay-as-you-go) so Cloud Functions can run. On the Spark (free) plan you can still use everything else (jobs, banners).

To enable push from this admin:

1. Upgrade the project to Blaze: Usage and billing → Modify plan. You only pay for what you use; the free quotas are generous.
2. From web-admin run: cd functions && npm install && cd .. && firebase deploy to deploy the sendNotificationToAll function.

Your app is already set up to receive (subscribed to topic "all"). Once the function is deployed, the Send form will work.