Smart thermostat shows E19 and cannot control the heating schedule; app schedules are ignored.

Safety first: No electrical risk; this is a software/configuration issue.

• Check online status: Ensure the thermostat and Internet Bridge show as online in the app.
• Force schedule refresh: In the app, temporarily disable the Smart Schedule for the affected room, save, then re-enable and save again.
• Restart devices: Power-cycle the Internet Bridge and remove/reinsert the thermostat batteries to force a resync.
• Update app and firmware: Confirm you are using the latest app version and that the devices have had time to receive firmware updates.
• Test manual control: Try changing the setpoint manually on the thermostat and in the app to confirm bidirectional communication.