If your Mysas have recently disconnected from WiFi, and you notice a down arrow (or an upside-down triangle) on the thermostat, then you'll need to re-connect to WiFi through the Mysa app.
1. Open the Mysa app and tap the sidebar menu
2. Tap "add thermostat" and follow the steps in the app to get it online.
Mysa keeps failing when I try to re-add it
Follow the steps listed in this article to get it back online.