As of August 29th, libslackrtm cannot post messages to enterprise Slack workspaces. Failures are as follows:
{"ok":false,"reply_to":3,"error":{"msg":"cannot process message","code":4,"source":"gatewayserver-REDACTED"}}
Recently, this was finally reported to Slack, for more insight on why this error is occurring.
Possible workaround is to use the more modern web API (conversions.post method) in order to post messages, but this should work, according to the documentation. Currently waiting to hear back again.
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