Firebase FCM returning 403 SenderId mismatch PERMISSION_DENIED while trying to push a notification

I'm trying to setup a dev environment for developing with FCM and I'm getting this error. I'm using the configuration of out-of-box and it is been loaded properly (I've debugged). I'm working with java 8 and spring 2.2.12 and firebase-admin 7.1.0.

com.google.api.client.http.HttpResponseException: 403 Forbidden
POST https://fcm.googleapis.com/v1/projects/projectt-82004/messages:send
{
  "error": {
    "code": 403,
    "message": "SenderId mismatch",
    "status": "PERMISSION_DENIED",
    "details": [
      {
        "@type": "type.googleapis.com/google.firebase.fcm.v1.FcmError",
        "errorCode": "SENDER_ID_MISMATCH"
      }
    ]
  }
}

What I've tried so far

• Create a new project and a new key
• There was an old documented error where the services were not activated by default. I've checked the services and all of them are active.
• Also, the user appears to have enough privileges.
• I've also updated the library to the latest version (it also happened with the previous version)

Am I missing something here?

UPDATE

Same code, later on the following day, without any changes to the code, it started working. So the conclusion was that there was some problem with the service itself.