Diagnosis
Error E1 indicates a short cycle or flame lockout error detected from your furnace's control board.
How to Fix It
This is a system error, not a thermostat fault. Turn off power to your furnace at the breaker for 60 seconds. Restore power. The thermostat should reset and the E1 code should clear after the furnace completes a startup cycle.
If That Didn't Work
The error is originating from the furnace. Common causes are a dirty flame sensor or a faulty pressure switch. These require furnace maintenance.
Heads Up
If E1 returns immediately, the thermostat is correctly relaying an error from your furnace. Do not bypass it; diagnose the furnace problem.