I'd verify your certificates are up to date (process described above). IMO, the easiest way to determine if the issue is the RPi or HG is to manually send a message via sending the commands yourself from a terminal window. If you can get it to work manually from the RPi where HG is installed, then the issue is HG. If you can't get it to work manually, that's the first thing to figure out. HG will never work if you can't send a message manually.