"Invalid client id specified on " on broadcast call

[dvis003]

I've been following both this and (hello-world) tutorial from which the Broadcast method was copied.
In both instances the call to https://api.twitch.tv/extensions/message/${channelId}
returns {"error":"Bad Request","status":400,"message":"Invalid client id specified"}
I am using clientID, ownerID and secret straight out of Dev Rig in both cases.
The Dev Rig generated keys are as follows:
EXT_CLIENT_ID: ej8Iwp02QO0sOlswrIO5sDrC5Khr6U
EXT_SECRET: kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
EXT_OWNER_ID: 402464751
At total loss why is it happening.