"Client not found" on PubSub send

Hello. I am trying to send a PubSub message, but getting the error “404, Client Not Found” message.
I am using a valid JWT and Client-Id.

Response:
{"error":"Not Found","status":404,"message":"{\n \"status\": 404,\n \"message\": \"Client not found\",\n \"error\": \"Not Found\"\n}"}

I guess this means that the channel id in the URL “was not found”, but the channel id is correct, so I don’t know why I get this message. Maybe the extension has to be “released” and not in “testing” stage?

The body looks like this:
{"content_type":"application/json", "message":"{\"foo\":\"bar\"}", "targets":["broadcast"]}

Help is appreciated!

Edit:
An explanation on the docs page for unfounded errors like this would help a lot.

No it means you are using the wrong clientID.

You need the ClientID from your Extension:

Not a ClientID that is for a “application”, but the ClientID for the Extension you are trying to Broadcast to

Yeah, thanks! I messed up the API client id and the extensions client id.