Elsewhere here I observed hundreds are reporting similar difficulties since upgrading to iOS 16.
My workaround that I seem to be having luck with is to only use simplified Automations as triggers for Scenes. (I suspect elaborate Automations get confused and won’t always work in iOS 16.)
First I deleted my ineffective Automation. Then, I use Scenes to create the end result I want. I finally create an Automation whose only purpose is to trigger the Scene I want.
Example: At home with security disarmed, when someone uses my home’s doors I like to hear a car-alarm single chirp when it opens, and a double-chirp when it closes. So I created two ‘Scenes’ (“Door Open” and “Door Close”): I have HomePod play the relevant ‘song’ from a sound-effect album in my Music library. Then I created an Automation so when my Aqara door sensor detects an open door, it triggers the Scene to play the correct chirp ‘Scene’ on HomePod. (It’s actually also simpler than setting up separate lengthy Automations for every door—the Scenes playing the chirp can be used for multiple Automations, one Automation trigger for each door.)
Fred