404 error for Firebase Cloud Messaging clients sending to a URL with a trailing slash

This incident has been resolved.

The rollback is complete - service is fully restored.

A recent change is causing 404 errors for clients who send messages to a URL which includes a trailing slash (/v1/projects/my-project/messages:send/ vs /v1/projects/my-project/messages:send). We are in the process of rolling back this change. For clients that are impacted, removing the trailing slash from the send URL will immediately resolve the problem.