Thermostat display shows E01 and will not connect to Wi‑Fi or the Mysa app.

Safety first: Turn off power to the thermostat at the breaker before removing it from the wall or accessing wiring. Do not work on live line-voltage circuits.

Steps to try:

• Power cycle the thermostat: Turn the heater/thermostat breaker OFF for 2 minutes, then back ON. Wait 3–5 minutes to see if E01 clears.
• Reset network settings: From the Mysa thermostat menu, go to Settings > Wi‑Fi > Reset (wording may vary by model). Then re-open the Mysa app and run the setup process again on a 2.4 GHz network.
• Check router settings: Ensure the 2.4 GHz band is enabled, SSID is visible, and security is WPA2 or WPA3. Disable MAC filtering or add the thermostat’s MAC address to the allowed list.
• Test with a mobile hotspot: Temporarily create a 2.4 GHz hotspot from a phone and try pairing. If E01 persists even with a known-good network, the Wi‑Fi module is likely faulty.
• Inspect for moisture or damage: With power OFF, remove the thermostat from the wall plate and check the PCB for signs of moisture, corrosion, or burn marks near the Wi‑Fi chip/antenna area.

If E01 will not clear after network reset, power cycling, and hotspot testing, the Wi‑Fi radio on the main logic board is likely defective and the thermostat should be replaced.