Hello. Today i came back home and none of my automations worked. so i looked whats wrong and i have got a notification of some error. Does someone know whats wrong. 
This happened to me recently too. It means there’s a device in your automations.yaml that it can’t find.
This is what I did to fix it: Look in the Home Assistant log for the device ID mentioned before the automation.yaml load error. Then edit automations.yaml and search for that ID. Delete that ID from automations.yaml, then restart HA.