Thermostat shows E08 and cannot complete firmware update or behaves erratically after an update attempt.

Safety first: No wiring changes are required, but avoid cycling power repeatedly during update attempts.

Steps to resolve:

• Ensure stable power and Wi‑Fi: Confirm the breaker is not tripping and Wi‑Fi signal is strong at the thermostat location.
• Retry firmware update: In the Mysa app, check for available firmware updates and attempt the update again, keeping the app open and phone nearby.
• Power cycle once: If the thermostat is frozen, turn the breaker OFF for 2 minutes, then ON, and allow the device to boot fully before retrying the update.
• Avoid repeated resets: Multiple rapid power cycles can worsen memory corruption. If E08 persists after one clean power cycle and update attempt, do not continue forcing updates.

Persistent E08 indicates flash memory or the bootloader on the main control board is corrupted. Field repair is not practical; the thermostat should be replaced.