FCM getting MismatchSenderId

Question

I have an application that uses Google FCM for sending push notifications.

When i send a push notification to a group of users, i get a response of MismatchSen

Answer 1

I wasted days on this.

In my case, I followed this blog to use Postman and get the mismatchsenderid error. Previously, I was getting messaging/mismatched-credential, and people reported that their client app used multiple projects.

However, for me, I have one-to-one, a web app and a project. BUT, I host all apps via ng serve on default port 4200. So regardless of what project / app pair I was developing on, I would always get the same token from my client web app using AngularFireMessaging.requestToken - this token was always the token created on my first ever run of a firebase app in development.

As a work around, I start different apps / projects on different ports and get proper tokens for respective projects.