First off, you’ve just exposed your OAuth token. Please revoke that token immediately. OAuth tokens are private information, and as per the Developer Agreement you have a responsibility to keep them private.
Secondly, you’re not listening for any error messages you may be getting. If sending isn’t successful it could be because your attempting to send messages in a channel that is in sub mode, or maybe it has a requirement for you to be following the channel, both of which would explain why it works when the bot is in its own channel but not in the other channel.
Also, I think whatever documentation you have been working off must be quite old because the cluster param hasn’t been needed for like a year or two.