"Requested entity was not found" when writing on Google Home Graph

Question

I'm trying to update the state of a device using Google Home Graph API, but I'm getting this reply and I don't understand why:

{
  "error": {
    "code": 404,
    "message": "Requested entity was not found.",
    "status": "NOT_FOUND"
  }
}

This is the first part of my SYNC reponse:

{
    "requestId": "reqId",
    "payload": {
        "agentUserId": "myAgentUserId",
        "devices": [
            {
                "id": "myDeviceId",
...
}

and this is what I'm sending to

https://homegraph.googleapis.com/v1/devices:reportStateAndNotification

{
    "agentUserId": "myAgentUserId",
    "payload": {
        "devices": {
            "states": {
                "myDeviceId": {
                    "on": true
...
}

As you can see, both myAgentUserId and myDeviceId in Home Graph's request are the same to the ones returned to the SYNC request.

What am I doing wrong?