# 40183: FCM service account required for FCM topics

Identifier: `fcm_service_account_required_for_topics`



An FCM topics request was refused because FCM topics require the app's FCM credentials to be a service account, but the app is configured only with a legacy FCM server key.

## What you should do

[Configure the app's FCM credentials](https://ably.com/docs/push/configure/device.md#fcm) with a Firebase service account key, in place of the legacy server key. Upload the key's JSON file in the app's [notification settings](https://ably.com/accounts/any/apps/any/notifications), or with the [Ably CLI](https://ably.com/docs/cli/push/config/set-fcm.md). The request then succeeds without any other change. Retrying the request does not help while the app has only a server key.

## Why it happens

FCM topics are managed and sent to through the FCM HTTP v1 APIs, which authenticate with a service account. A legacy server key can't be used with them, so Ably refuses the request before contacting FCM rather than failing it later.

## What you'll see

The error is reported with code 40183 and HTTP status 400. The message is `unable to use FCM topics; FCM topics require the app's FCM credentials to be a service account, not a legacy server key`.