Safety first: No mains exposure is required to troubleshoot this fault.

Check app time sync: Ensure your phone and Wiser account have the correct time zone. In many Wiser systems, the hub syncs time to the thermostat.
Reboot Heat Hub and thermostat: Power-cycle the Heat Hub and remove/reinsert the thermostat or its batteries.
Recreate schedules: Delete existing schedules in the app and create a simple test schedule. Observe whether it is retained after a power cycle.
Firmware update: Use the app to check for and install any available firmware updates for the Heat Hub and thermostat.
If E10 persists: The internal clock or memory is likely defective. Replace the thermostat.

Thermostat shows E10 and schedules do not run; time and date keep resetting

Possible Causes