I Think there are number of different things it can cause these issues, which is one reason they are so hard to pin down.
The first question, of course, is the presence sensor being recognized. You’ve probably already seen this one, but here’s the steps to go through to verify that
There used to be a problem with routines where if a routine set the mode, but the house is already in the mode that it was going to be set to, then nothing for that routine worked. This was a very common issue for people who had more than one person listed as arriving for the same routine.
I think this was later fixed for a while, but I have begun to wonder if the same issue has come back. I haven’t had time to test it myself, but I just mention it as something to consider. In addition, the fix to this approach is to break out your routines so that you have one per presence indicator and that can really help with troubleshooting.
I hadn’t previously heard about the issues with harmony or nest or other third-party services, but there may be a synchronization issue going on.
I wish I had an easy answer but there doesn’t seem to be one.
