Location based homekit automation is not triggering
I was fighting this exact same problem for a while, myself - everything except location automation was functioning.  My troubles were in my iCloud settings - my location was determined based on a device which was no longer in service, instead of my iPhone.  So, HomeKit interpreted things as if I was always away from home.  After updating the location settings to track on my iPhone, the automations fired back up properly again.  

Hopefully this helps a few others out, ha.